Make GitHub Actions workflow more secure (#2154)

Co-authored-by: Sindre Sorhus <[email protected]>

Author: ashishkurmi

.github/workflows/main.yml

@@ -2,6 +2,8 @@ name: CI
 on:
   - push
   - pull_request
+permissions:
+  contents: read
 jobs:
   test:
     name: Node.js ${{ matrix.node-version }} on ${{ matrix.os }}