docs: add README

Author: EndBug

README.md

@@ -0,0 +1,37 @@
+# label-sync
+An action that allows you to sync labels from a repository or a config file.
+
+### Example workflow:
+
+```yaml
+name: Sync labels
+on: 
+  # You can run this with every type of event, but it's better to run it only when you actually need it.
+  workflow_dispatch:
+  
+jobs:
+  labels:
+    runs-on: ubuntu-latest
+    
+    steps:
+    - uses: EndBug/label-sync@v1
+      with:
+        # This is needed in order to edit the labels
+        token: ${{ secrets.GITHUB_TOKEN }}
+        
+        # If you want to use a config file, you can put its path here
+        config-file: .github/labels.yml
+
+        # If you want to use a source repo, you can put is name here (only the owner/repo format is accepted)
+        source-repo: owner/repo
+        # If you're using a private source repo, you'll need to add a custom token for the action to read it
+        source-repo-token: ${{ secrets.YOUR_OWN_SECRET }}
+
+        # If you want to delete any additional label, set this to true
+        delete-other-labels: false
+
+        #If you want the action just to show you the preview of the changes, without actually editing the labels, set this to tru
+        dry-run: true
+```
+
+This is only a sample workflow to illustrate all the options: if you want to see an actual workflow you can check the one in this repo [here](.github/workflows/labels.yml).