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/README.md

@@ -0,0 +1,84 @@
+# InvenTree Documentation
+
+[![Documentation Status](https://readthedocs.org/projects/inventree/badge/?version=latest)](https://inventree.readthedocs.io/en/latest/?badge=latest)
+
+This repository hosts the [official documentation](https://inventree.readthedocs.io/) for [InvenTree](https://github.com/inventree/inventree), an open source inventory management system.
+
+To serve this documentation locally (e.g. for development), you will need to have Python 3 installed on your system.
+
+## Setup
+
+Run the following commands from the top-level project directory:
+
+```
+$ git clone https://github.com/inventree/inventree
+$ cd inventree/docs
+$ pip install -r requirements.txt
+```
+
+## Serve Locally
+
+To serve the pages locally, run the following command (from the top-level project directory):
+
+```
+$ mkdocs serve -a localhost:8080
+```
+
+## Edit Documentation Files
+
+Once the server is running, it will monitor the documentation files for any changes, and update the served pages.
+
+### Admonitions
+
+"Admonition" blocks can be added as follow:
+```
+!!! info "This is the admonition block title"
+    This is the admonition block content
+```
+
+Refer to the [reference documentation](https://squidfunk.github.io/mkdocs-material/reference/admonitions/) to customize the admonition block to the use-case (eg. warning, missing, info, etc.).
+
+### Internal Links
+
+Links to internal documentation pages **must** use relative pathing, otherwise the link will be broken by the readthedocs URL formatting.
+
+Also, linking to an internal page must use the `.md` suffix!
+
+For example, to link to the page `/part/views` from `/stock/stocktake`, the link must be formed as follows:
+
+```
+Click [here](../part/views.md)
+```
+
+*Formatting the link as follows:*
+
+```
+Click [here](/part/views)
+```
+
+*will result in a broken link.*
+
+### Images
+
+Images are served from the `./docs/assets/images` folder and can be added as follow:
+```
+{% with id="image_id", url="folder/image_name.png", description="Text shown if image is not loaded properly" %}
+{% include 'img.html' %}
+{% endwith %}
+```
+
+Replace:
+* `image_id` with a short unique indentifier for the image (most commonly, `image_id` is same as `image_name`)
+* `folder` with the folder in `docs/assets/images` in which the image is stored
+* `image_name` with the name of the image
+* `.png` with the image extension (PNG or JPEG are preferred formats)
+
+### Global variables
+
+Refer to the [reference documentation](https://squidfunk.github.io/mkdocs-material/reference/variables/#using-custom-variables) to find out how to add global variables to the documentation site.
+
+Global variables should be added in the `# Global Variables` section of the `mkdocs.yml` configuration file.
+
+## Credits
+
+This documentation makes use of the [mkdocs-material template](https://github.com/squidfunk/mkdocs-material)