Do not require user provided githubToken input (configure default) (#7)

* Do not require user provided `githubToken` input  (configure default)

* Remove `edited` from workflow example

Idea of this example was to show setup where CI runs only when particular files are changed. Triggering workflow when name or description of PR is edited is not needed for this use case.

action.yml

@@ -5,6 +5,7 @@ inputs:
   githubToken:
     description: 'GitHub Access Token'
     required: true
+    default: ${{ github.token }}
   filters:
     description: 'YAML dictionary where keys specifies rule names and values are lists of (globbing) file path patterns'
     required: true