Remove some options and add docs

* Remove the unused CondifGir option
  * Add docs for the default section
  * Move some docs from other files

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

doc/webhooks.md

@@ -0,0 +1,27 @@
+# Webhooks
+
+Garm is designed to auto-scale github runners. To achieve this, ```garm``` relies on [GitHub Webhooks](https://docs.github.com/en/developers/webhooks-and-events/webhooks/about-webhooks). Webhooks allow ```garm``` to react to workflow events from your repository, organization or enterprise.
+
+In your repository or organization, navigate to ```Settings --> Webhooks```. In the ```Payload URL``` field, enter the URL to the ```garm``` webhook endpoint. The ```garm``` API endpoint for webhooks is:
+
+  ```txt
+  POST /webhooks
+  ```
+
+If ```garm``` is running on a server under the domain ```garm.example.com```, then that field should be set to ```https://garm.example.com/webhooks```.
+
+In the webhook configuration page under ```Content type``` you will need to select ```application/json```, set the proper webhook URL and, really important, **make sure you configure a webhook secret**. Garm will authenticate the payloads to make sure they are coming from GitHub.
+
+The webhook secret must be secure. Use something like this to generate one:
+
+  ```bash
+  gabriel@rossak:~$ function generate_secret () {
+      tr -dc 'a-zA-Z0-9!@#$%^&*()_+?><~\`;' < /dev/urandom | head -c 64;
+      echo ''
+  }
+
+  gabriel@rossak:~$ generate_secret
+  9Q<fVm5dtRhUIJ>*nsr*S54g0imK64(!2$Ns6C!~VsH(p)cFj+AMLug%LM!R%FOQ
+  ```
+
+Next, you can choose which events GitHub should send to ```garm``` via webhooks. Click on ```Let me select individual events``` and select ```Workflow jobs``` (should be at the bottom). You can send everything if you want, but any events ```garm``` doesn't care about will simply be ignored.