Restructure headscale documentation (#2163)

* Setup mkdocs-redirects

* Restructure existing documentation

* Move client OS support into the documentation

* Move existing Client OS support table into its own documentation page
* Link from README.md to the rendered documentation
* Document minimum Tailscale client version

* Reuse CONTRIBUTING.md" in the documentation

* Include "CONTRIBUTING.md" from the repository root
* Update FAQ and index page and link to the contributing docs

* Add configuration reference

* Add a getting started page and explain the first steps with headscale

* Use the existing "Using headscale" sections and combine them into a
  single getting started guide with a little bit more explanation.
* Explain how to get help from the command line client.
* Remove duplicated sections from existing installation guides

* Document requirements and assumptions

* Document packages provided by the community

* Move deb install guide to official releases

* Move manual install guide to official releases

* Move container documentation to setup section

* Move sealos documentation to cloud install page

* Move OpenBSD docs to build from source

* Simplify DNS documentation

* Add sponsor page

* Add releases page

* Add features page

* Add help page

* Add upgrading page

* Adjust mkdocs nav

* Update wording

Use the term headscale for the project, Headscale on the beginning of a
sentence and `headscale` when refering to the CLI.

* Welcome to headscale

* Link to existing documentation in the FAQ

* Remove the goal header and use the text as opener

* Indent code block in OIDC

* Make a few pages linter compatible

Also update ignored files for prettier

* Recommend HTTPS on port 443

Fixes: #2164

* Use hosts in acl documentation

thx @efficacy38 for noticing this

Ref: #1863

* Use mkdocs-macros to set headscale version once

docs/usage/connect/android.md

@@ -0,0 +1,14 @@
+# Connecting an Android client
+
+This documentation has the goal of showing how a user can use the official Android [Tailscale](https://tailscale.com) client with headscale.
+
+## Installation
+
+Install the official Tailscale Android client from the [Google Play Store](https://play.google.com/store/apps/details?id=com.tailscale.ipn) or [F-Droid](https://f-droid.org/packages/com.tailscale.ipn/).
+
+## Configuring the headscale URL
+
+- Open the app and select the settings menu in the upper-right corner
+- Tap on `Accounts`
+- In the kebab menu icon (three dots) in the upper-right corner select `Use an alternate server`
+- Enter your server URL (e.g `https://headscale.example.com`) and follow the instructions