Consider updating documentation for changelog generation in release process section of CONTRIBUTING.md

[Rosalita]

Our release process currently has a dependency on a developer having a working Ruby tool chain in order to generate release notes. There’s been a few times where SDK developers have had issues with their ruby toolchains which has ended up being a blocker for releasing.

Since this release process was written, Github have added a changelog generator to their UI. We should consider moving to this rather than depending on the ruby gem github_changelog_generator

Acceptance criteria:

• Update CONTRIBUTING.md to explain the process required to generate a changelog using the GitHub UI
• Rather than pushing the tag to GitHub, the option to tell GitHub to create a new tag on release should be used.

┆Issue is synchronized with this Jira Task by Unito

[Rosalita]

@QuintinWillison @AndyNicks it would be good to get your thoughts

Example of changelog output generated by GitHub UI

## What's Changed
* v1.2 event emitter for connection (RTN4) by @tcard in https://github.com/ably/ably-go/pull/144
* Add rtn16  by @gernest in https://github.com/ably/ably-go/pull/165
* Add RTN23- heartbeats by @gernest in https://github.com/ably/ably-go/pull/169
* remove unused fields from Connection by @gernest in https://github.com/ably/ably-go/pull/171
* Rename master to main by @QuintinWillison in https://github.com/ably/ably-go/pull/167
* v1.2 ChannelOptions by @tcard in https://github.com/ably/ably-go/pull/146
* v1.2 ClientOptions by @tcard in https://github.com/ably/ably-go/pull/145
* Fix instances of old nil *ChannelOptions becoming nil option func. by @tcard in https://github.com/ably/ably-go/pull/173
* Have a single Travis build as originally intended. by @tcard in https://github.com/ably/ably-go/pull/176
* proto: Decode ms durations as a time.Duration wrapper. by @tcard in https://github.com/ably/ably-go/pull/174
* Temporarily skip test for RTN23. by @tcard in https://github.com/ably/ably-go/pull/178
* RTN15i: Add test for already existing functionality. by @tcard in https://github.com/ably/ably-go/pull/180
* Fix data race in RTN23 test. by @tcard in https://github.com/ably/ably-go/pull/177
* Fix race condition in RTN15i test by @tcard in https://github.com/ably/ably-go/pull/182
* RTN15g: Don't attempt resume after server has discarded state by @tcard in https://github.com/ably/ably-go/pull/181
* RTN15h*: Handle incoming DISCONNECTED while CONNECTED by @tcard in https://github.com/ably/ably-go/pull/179
* Fix test for Heartbeat by @gernest in https://github.com/ably/ably-go/pull/183
* RTL13: Handle DETACHED while not DETACHING. by @tcard in https://github.com/ably/ably-go/pull/185
* RTN15e: Check that Connection.Key changes on reconnections. by @tcard in https://github.com/ably/ably-go/pull/188
* RTN15d: Add a test for message delivery on connection recovery. by @tcard in https://github.com/ably/ably-go/pull/187
* RTL2: EventEmitter for channel events; remove old State by @tcard in https://github.com/ably/ably-go/pull/190
* Handle non-PaginatedResult but otherwise valid HTTP error responses by @tcard in https://github.com/ably/ably-go/pull/194
* Add HTTPRequestTimeout option with 10s default by @tcard in https://github.com/ably/ably-go/pull/193
* Merge main into 1.2 by @tcard in https://github.com/ably/ably-go/pull/196
* Always include serial values in encoded protocol messages by @lmars in https://github.com/ably/ably-go/pull/195
* Ad-hoc fix for enqueuing attach attempt when DISCONNECTED. by @tcard in https://github.com/ably/ably-go/pull/191
* Explicitly annotate enum vars so that godoc places them with the type by @tcard in https://github.com/ably/ably-go/pull/200
* Introduce ErrorCode type for predefined error codes by @tcard in https://github.com/ably/ably-go/pull/199
* Remove things from public API that aren't in the spec by @tcard in https://github.com/ably/ably-go/pull/201
* v1.2-compliant message and presence publish and subscribe by @tcard in https://github.com/ably/ably-go/pull/202
* Implement options as package-level functions by @tcard in https://github.com/ably/ably-go/pull/205
* Update README for 1.2 preview, with associated fixes by @tcard in https://github.com/ably/ably-go/pull/206
* add rtn14 - Connection opening failures: by @gernest in https://github.com/ably/ably-go/pull/172
* RTL6c: Publish while not connected by @tcard in https://github.com/ably/ably-go/pull/208
* Add RTN2g by @gernest in https://github.com/ably/ably-go/pull/210
* Add examples for handling events and errors by @lmars in https://github.com/ably/ably-go/pull/265
* Add maintainers file by @niksilver in https://github.com/ably/ably-go/pull/267
* add RTN19 - Transport state side effect by @gernest in https://github.com/ably/ably-go/pull/170
* Fix regression in TestAuth_ClientID's flakiness. by @tcard in https://github.com/ably/ably-go/pull/272
* Replace Travis with GitHub workflow by @QuintinWillison in https://github.com/ably/ably-go/pull/273
* Merge main into 1.2 by @tcard in https://github.com/ably/ably-go/pull/274
* Minor changes for 1.2 API compliance by @tcard in https://github.com/ably/ably-go/pull/270
* Propagate contexts everywhere by @tcard in https://github.com/ably/ably-go/pull/276
* Bump the version constants by @lmars in https://github.com/ably/ably-go/pull/280

## New Contributors
* @niksilver made their first contribution in https://github.com/ably/ably-go/pull/267

**Full Changelog**: https://github.com/ably/ably-go/compare/v1.1.5...v1.2.0-apipreview.4

[AndyNicks]

The Git tool has some limitations. I would like the report to have at least a “closed questions” section.