Add and configure ESLint and update configuration for Prettier (#508)

* Add ESLint and update Prettier

* Rebuild action

* Update package.json

src/labeler.ts

@@ -19,7 +19,7 @@ export async function run() {
 
     const prNumber = getPrNumber();
     if (!prNumber) {
-      console.log('Could not get pull request number from context, exiting');
+      core.info('Could not get pull request number from context, exiting');
       return;
     }