Added global lua function CreateInvalidObject (#652)

[igromanru]

Resolves #652

Testing
Built UE4SS and deployed in Abiotic Factor.
Tested with Lua code:

local blankObject = CreateBlankObject()
print("blankObject varibale type: " .. type(blankObject))
if blankObject then
	print("blankObject userdata type: " .. blankObject:type())
	print("blankObject IsValid:" .. tostring(blankObject:IsValid()))
end

Result:

[12:40:32.1231285] [Lua] blankObject varibale type: userdata
[12:40:32.1231360] [Lua] blankObject userdata type: UObject
[12:40:32.1231428] [Lua] blankObject IsValid:false

Additional
Fixed FindFirstOf return type annotation in Types.lua

Documentation
All changes documented in Changelog.md and created a new docs page for CreateBlankObject.

[igromanru]

Can someone just Clone the branch from my fork, compile and test it locally, then just force merge?
Also please squash commits while merging.

[narknon]

I think "Blank" is a bit confusing. Maybe dummy or empty?

[UE4SS]

I think "Blank" is a bit confusing. Maybe dummy or empty?

Perhaps "CreateInvalidObject" is even more accurate to what the function actually does ?

[narknon]

I guess CreateInvalidLuaUObject is too verbose

[UE4SS]

I guess CreateInvalidLuaUObject is too verbose

Yeah I don't think "LuaU" is necessary, and besides, we might reuse this function at some point for non-UObject stuff so it's nice to keep the "U" out of "Object".
It really doesn't have anything to do with UObject anyway, it's just a function implemented for UObjects among other objects.

[narknon]

Yeah. I guess CreateInvalidObject works.

[igromanru]

Tested;

local invalidObject = CreateInvalidObject()
print("blankObject variable type: " .. type(invalidObject))
if invalidObject then
	print("blankObject userdata type: " .. invalidObject:type())
	print("blankObject IsValid: " .. tostring(invalidObject:IsValid()))
end

Result:

blankObject variable type: userdata
blankObject userdata type: UObject
blankObject IsValid: false