ci(test): run on pull request and add concurrency configuration (#17)

- Run test on pull requests to the main branch instead of on every push
- Cancel in-progress workflows if a PR is updated (i.e., a new commit is
pushed) and the same workflows are triggered to run again
- Rename step ID from `demo` to `test`

---------

Co-authored-by: Gregor Martynus <[email protected]>

.github/workflows/test.yml

@@ -1,5 +1,10 @@
 name: test
-on: [push]
+on:
+  pull_request:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 
 jobs:
   test:
@@ -13,14 +18,14 @@ jobs:
       - run: npm ci
       - run: npm run build
       - uses: ./ # Uses the action in the root directory
-        id: demo
+        id: test
         with:
           app_id: ${{ vars.TEST_APP_ID }}
           private_key: ${{ secrets.TEST_APP_PRIVATE_KEY }}
       - uses: octokit/[email protected]
         id: get-repository
         env:
-          GITHUB_TOKEN: ${{ steps.demo.outputs.token }}
+          GITHUB_TOKEN: ${{ steps.test.outputs.token }}
         with:
           route: GET /installation/repositories
       - run: echo '${{ steps.get-repository.outputs.data }}'