ci.yml: fix workflow trigger (#19)

* ci.yml: fix workflow trigger

* specify node version

* upgrade setup-node step

* simplify

.github/workflows/ci.yml

@@ -2,27 +2,24 @@ name: CI checks
 
 on:
   push:
-    branches: [$default-branch]
+    branches: [main]
   pull_request:
-    branches: [$default-branch]
+    branches: [main]
 
 jobs:
   checks:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-node@v3
+      - uses: actions/setup-node@v4
         with:
+          node-version: 18
           cache: 'npm'
       - run: npm ci
-      - name: Typecheck
-        run: npm run typecheck
-      - name: Lint code
-        run: npm run lint
-      - name: Lint docs
-        run: npm run lint:docs
-      - name: Tests
-        run: npm run test
+      - run: npm run typecheck
+      - run: npm run lint
+      - run: npm run lint:docs
+      - run: npm run test
       - name: Check that commit contains build artifacts
         run: |
           npm run build