Problem: Missing cpp library documents for developers

[damoncro]

Last Friday, discussed with @lezzokafka @ricky321q.

The suggestions:

1. Add source codes examples in comments and export to a draft (markdown/html) first.
2. Study Rust Doc comments way to generate final cpp documents based on markdown/html templates.
3. Add Unreal documents in the workflow.

[damoncro]

Suggestions on slack: https://devblogs.microsoft.com/cppblog/clear-functional-c-documentation-with-sphinx-breathe-doxygen-cmake/

[damoncro]

And https://slint-ui.com/releases/0.2.1/docs/cpp/

[damoncro]

https://github.com/TartanLlama/cpp-documentation-example