[CI SKIP] improve CONTRIBUTING.md (#3443)
[CI SKIP] improve CONTRIBUTING.md (#3443)

* update Useful knowledge

* update extension workflow

* move disclaimer

* capitalize sentence beginnings

* Update CONTRIBUTING.md

* improve debugging info

* Update CONTRIBUTING.md

* remove info about CatalogSource

* Update CONTRIBUTING.md

* fix typo

* restructure a sentence

* Update CONTRIBUTING.md

* new unearthed info!

* explain SourceFactory, other minor corrections

* restructure the text in a more meaningful way

* remove redundancy

* correct grammar error

* Update CONTRIBUTING.md

* Update CONTRIBUTING.md

* update document header

* Update CONTRIBUTING.md

* Update CONTRIBUTING.md

* Update CONTRIBUTING.md

* Update CONTRIBUTING.md

* remove disclaimer section

* Update CONTRIBUTING.md

* Update CONTRIBUTING.md
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