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/docs/index.md

@@ -0,0 +1,18 @@
+---
+title: InvenTree
+template: home.html
+hide:
+    - toc
+---
+
+## Intuitive Inventory Management
+
+
+InvenTree is an open-source inventory management system which provides intuitive parts management and stock control.
+
+
+It is designed to be lightweight and easy to use for SME or hobbyist applications. Powerful business logic works in the background to ensure that stock tracking history is maintained, and users have ready access to stock level information. InvenTree is designed to allow for a flexible installation.
+
+InvenTree is a [Python](https://www.python.org/) and [Django](https://www.djangoproject.com/) application which stores data in a relational database, and serves this data to the user(s) via a web browser, and (optionally) can be integrated into custom applications via an API.
+
+----------------------