docs: GitHub PAT authentication

docs/authentication.md

@@ -2,12 +2,24 @@
 
 ### GitLab
 
-Currently, only the GitLab [personnal access
+You need to create a [personnal access
 token](https://docs.gitlab.com/ee/user/profile/personal_access_tokens.html)
-is supported. The file path containing the access tokenfor a remote is
-provided with the attribute `comin.remotes.*.auth.access_token_path`.
+and store this token into a file (`/filepath/to/your/access/token` in the below example). 
 
-Example:
+### GitHub
+
+You need to create a [fined-grained personnal access
+token](https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/managing-your-personal-access-tokens#fine-grained-personal-access-tokens)
+and store this token into a file (`/filepath/to/your/access/token` in
+the below example). Note classic personal access tokens are also
+supported.
+
+### Use your personal access token
+
+The file path containing this access token for a remote is provided
+with the attribute `comin.remotes.*.auth.access_token_path`.
+
+#### Example
 
 ```nix
 services.comin = {