Misc doc fixes (#2240)

* Link back to node registration docs
* adjust wording in apple docs
* Mention client specific page to check if headscale works

Ref: #2238

docs/ref/acls.md

@@ -45,11 +45,11 @@ headscale server.
 
 ACLs have to be written in [huJSON](https://github.com/tailscale/hujson).
 
-When registering the servers we will need to add the flag
-`--advertise-tags=tag:<tag1>,tag:<tag2>`, and the user that is
-registering the server should be allowed to do it. Since anyone can add tags to
-a server they can register, the check of the tags is done on headscale server
-and only valid tags are applied. A tag is valid if the user that is
+When [registering the servers](../usage/getting-started.md#register-a-node) we
+will need to add the flag `--advertise-tags=tag:<tag1>,tag:<tag2>`, and the user
+that is registering the server should be allowed to do it. Since anyone can add
+tags to a server they can register, the check of the tags is done on headscale
+server and only valid tags are applied. A tag is valid if the user that is
 registering it is allowed to do it.
 
 To use ACLs in headscale, you must edit your `config.yaml` file. In there you will find a `policy.path` parameter. This will need to point to your ACL file. More info on how these policies are written can be found [here](https://tailscale.com/kb/1018/acls/).

docs/usage/connect/apple.md

@@ -60,7 +60,7 @@ Install the official Tailscale tvOS client from the [App Store](https://apps.app
 
 ### Configuring the headscale URL
 
-- Go Settings (the apple tvOS settings) > Apps > Tailscale
+- Open Settings (the Apple tvOS settings) > Apps > Tailscale
 - Under `ALTERNATE COORDINATION SERVER URL`, select `URL`
 - Enter the URL of your headscale instance (e.g `https://headscale.example.com`) and press `OK`
 - Return to the tvOS Home screen

docs/usage/getting-started.md

@@ -9,6 +9,8 @@ This page helps you get started with headscale and provides a few usage examples
       installation instructions.
     * The configuration file exists and is adjusted to suit your environment, see
       [Configuration](../ref/configuration.md) for details.
+    * Headscale is reachable from the Internet. Verify this by opening client specific setup instructions in your
+      browser, e.g. https://headscale.example.com/windows
     * The Tailscale client is installed, see [Client and operating system support](../about/clients.md) for more
       information.