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/apple-client.md

@@ -1,51 +0,0 @@
-# Connecting an Apple client
-
-## Goal
-
-This documentation has the goal of showing how a user can use the official iOS and macOS [Tailscale](https://tailscale.com) clients with `headscale`.
-
-!!! info "Instructions on your headscale instance"
-
-    An endpoint with information on how to connect your Apple device
-    is also available at `/apple` on your running instance.
-
-## iOS
-
-### Installation
-
-Install the official Tailscale iOS client from the [App Store](https://apps.apple.com/app/tailscale/id1470499037).
-
-### Configuring the headscale URL
-
-- Open Tailscale and make sure you are _not_ logged in to any account
-- Open Settings on the iOS device
-- Scroll down to the `third party apps` section, under `Game Center` or `TV Provider`
-- Find Tailscale and select it
-  - If the iOS device was previously logged into Tailscale, switch the `Reset Keychain` toggle to `on`
-- Enter the URL of your headscale instance (e.g `https://headscale.example.com`) under `Alternate Coordination Server URL`
-- Restart the app by closing it from the iOS app switcher, open the app and select the regular sign in option
-  _(non-SSO)_. It should open up to the headscale authentication page.
-- Enter your credentials and log in. Headscale should now be working on your iOS device.
-
-## macOS
-
-### Installation
-
-Choose one of the available [Tailscale clients for macOS](https://tailscale.com/kb/1065/macos-variants) and install it.
-
-### Configuring the headscale URL
-
-#### Command line
-
-Use Tailscale's login command to connect with your headscale instance (e.g `https://headscale.example.com`):
-
-```
-tailscale login --login-server <YOUR_HEADSCALE_URL>
-```
-
-#### GUI
-
-- ALT + Click the Tailscale icon in the menu and hover over the Debug menu
-- Under `Custom Login Server`, select `Add Account...`
-- Enter the URL of your headscale instance (e.g `https://headscale.example.com`) and press `Add Account`
-- Follow the login procedure in the browser