Run GitHub Actions tests on community PRs too

.github/workflows/build.yml

@@ -1,20 +1,11 @@
 name: Build and Test
-
-on:
-  push:
-    branches:
-      - '**'
-  pull_request:
-    branches:
-      - $default-branch
+on: [push, pull_request]
 
 jobs:
-
   build:
     name: Build
     runs-on: ubuntu-latest
     steps:
-
     - name: Set up Go 1.x
       uses: actions/setup-go@v2
       with: