Add .editorconfig file (#16795)

Summary of the issue:
Following the recent attempts to uniformize code style with linting, it makes sense to add an .editorconfig file, as this is the format that is widely supported by IDEs out of the box.
Visual Studio code insists on sticking to space indentation for new files and sometimes switches from tab to space indentation for Python files. This is fixed with .editorconfig and an editorconfig extension in Visual Studio code.
Description of user facing changes
Added .editorconfig

Description of development approach
.editorconfig file according to NVDA's code style.

.editorconfig

@@ -0,0 +1,12 @@
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+
+[*.{cpp,h,py}]
+charset = utf-8
+indent_style = tab
+tab_width = 4
+trim_trailing_whitespace = true
+max_line_length = 110

user_docs/en/changes.md

@@ -12,6 +12,8 @@
 
 Please refer to [the developer guide](https://www.nvaccess.org/files/nvda/documentation/developerGuide.html#API) for information on NVDA's API deprecation and removal process.
 
+* Added a `.editorconfig` file to NVDA's repository in order for several IDEs to pick up basic NVDA code style rules by default. (#16795, @LeonarddeR)
+
 #### Deprecations
 
 ## 2024.3