Documentation integration (#4653)

* Add documentation under docs/ directory

* Add CI workflow for mkdocs configuration checking

* Add documentation issue template

* update pip-tools?

* Update .gitignore files

* Fix .gitignore rules

* Improve release notes page

* remove references to old repo

docs/requirements.txt

@@ -0,0 +1,4 @@
+mkdocs-macros-plugin>=0.7,<1.0
+mkdocs-material>=9.0,<10.0
+mkdocs-git-revision-date-localized-plugin>=1.1,<2.0
+mkdocs-simple-hooks>=0.1,<1.0