ci: include built files in release commit

The npm version lifecycle hook rebuilds the project and stages the
output so that the semantic-release git commit includes up-to-date
built files (lib/main/index.js, README.md).

Co-authored-by: Copilot <[email protected]>

Author: dhensby

package.json

@@ -11,7 +11,8 @@
     "lint:fix": "npm run lint -- --fix",
     "prepare": "npm run build",
     "test": "mocha -r ts-node/register './test/**/**.ts'",
-    "test:coverage": "nyc --all npm run test --silent"
+    "test:coverage": "nyc --all npm run test --silent",
+    "version": "npm run build && git add README.md lib/"
   },
   "files": [
     "action.yml",