Update CI

.github/workflows/ci.yml

@@ -1,12 +1,16 @@
-name: My Workflow
+name: CI
 
 on:
-  pull_request:
   push:
+    branches:
+      - master
+  pull_request:
+    types:
+      - opened
+      - synchronize
 
 jobs:
   my_job:
-    name: My Job on ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
 
     strategy:
@@ -14,6 +18,6 @@ jobs:
         os: [ubuntu-latest, macos-latest]
 
     steps:
-      - uses: actions/checkout@v2
-      - uses: cachix/install-nix-action@v16
+      - uses: actions/checkout@v3
+      - uses: cachix/install-nix-action@v20
       - run: ./test.sh