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

README.md

@@ -46,31 +46,11 @@ buttons available in the repo.
 
 ## Features
 
-- Full "base" support of Tailscale's features
-- Configurable DNS
-  - [Split DNS](https://tailscale.com/kb/1054/dns/#using-dns-settings-in-the-admin-console)
-- Node registration
-  - Single-Sign-On (via Open ID Connect)
-  - Pre authenticated key
-- Taildrop (File Sharing)
-- [Access control lists](https://tailscale.com/kb/1018/acls/)
-- [MagicDNS](https://tailscale.com/kb/1081/magicdns)
-- Dual stack (IPv4 and IPv6)
-- Routing advertising (including exit nodes)
-- Ephemeral nodes
-- Embedded [DERP server](https://tailscale.com/blog/how-tailscale-works/#encrypted-tcp-relays-derp)
+Please see ["Features" in the documentation](https://headscale.net/about/features/).
 
 ## Client OS support
 
-| OS      | Supports headscale                                                                                 |
-| ------- | -------------------------------------------------------------------------------------------------- |
-| Linux   | Yes                                                                                                |
-| OpenBSD | Yes                                                                                                |
-| FreeBSD | Yes                                                                                                |
-| Windows | Yes (see [docs](./docs/windows-client.md) and `/windows` on your headscale for more information)   |
-| Android | Yes (see [docs](./docs/android-client.md))                                                         |
-| macOS   | Yes (see [docs](./docs/apple-client.md#macos) and `/apple` on your headscale for more information) |
-| iOS     | Yes (see [docs](./docs/apple-client.md#ios) and `/apple` on your headscale for more information)   |
+Please see ["Client and operating system support" in the documentation](https://headscale.net/about/clients/).
 
 ## Running headscale
 
@@ -99,7 +79,7 @@ Please read the [CONTRIBUTING.md](./CONTRIBUTING.md) file.
 ### Requirements
 
 To contribute to headscale you would need the latest version of [Go](https://golang.org)
-and [Buf](https://buf.build)(Protobuf generator).
+and [Buf](https://buf.build) (Protobuf generator).
 
 We recommend using [Nix](https://nixos.org/) to setup a development environment. This can
 be done with `nix develop`, which will install the tools and give you a shell.