docs: Move docs to MkDocs

[Neko-vecter]

Description

This pull request is move current docs and some improvements to MkDocs.

What in this pull request?

• It can be deployed on GitHub Pages.
• Better document translation and localization (it easier translation and localization to other languages)
• Easier to navigate and search
• Better document structure (find things much easier)

Screenshots/Recordings/Graphs

Build the docs

It able build using docker by using command below

# clone from the fork 
git clone https://github.com/Neko-vecter/OrcaSlicer.git
cd ~/OrcaSlicer
docker run --rm -it -v ${PWD}:/docs squidfunk/mkdocs-material build

The build site in site folder.

Others

The action still in progress.

Also the common issue I still being collected and organized. It will add in future pull request.

-Neko.vecter