fix: problem matcher path (#4)

fixes the action failing with

```
Unable to process command '::add-matcher::.github/deno-matcher.json' successfully.
Could not find file '/home/runner/work/$ORG/$REPO/.github/deno-matcher.json'.
```

action.yml

@@ -44,7 +44,7 @@ runs:
 
     - name: Register Deno problem matchers
       shell: bash
-      run: echo "::add-matcher::.github/deno-matcher.json"
+      run: echo "::add-matcher::${{ github.action_path }}/.github/deno-matcher.json"
 
     - name: Cache Deno dependencies
       id: cache-deno