Refine CONTRIBUTING.md (#10324)
Refine CONTRIBUTING.md (#10324)

* Slightly refine CONTRIBUTING.md

* Write more about run_spec

* Wording

* Deeper tests is an advanced topic. Move to bottom

* Mention prettier-regression-testing

* Fix the type for snippets

* Typo

* Add 'Advanced topics' heading

* Fix run_spec types

* Minor edits

* Add link

* Wording around yarn fix

* Update CONTRIBUTING.md

Co-authored-by: fisker Cheung <c7e5eb375c44f84a4c70ec3f9a94e81f662bb7f8@gmail.com>
jlongster/prettier,rattrayalex/prettier,prettier/prettier,prettier/prettier,prettier/prettier,prettier/prettier,rattrayalex/prettier,rattrayalex/prettier