chore: build updates

* Update test to build on main branch instead of master
* Update workflows to use actions/checkout@v2, which performs a
  shallow clone by default, so should be slightly faster

.github/workflows/comment_on_pull_request.yml

@@ -1,12 +1,12 @@
 name: Comment on Pull Request
 on:
-  - pull_request
+  pull_request:
 
 jobs:
   comment:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - uses: ./
         with:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/comment_on_push.yml

@@ -1,12 +1,12 @@
 name: Comment on Push
 on:
-  - push
+  push:
 
 jobs:
   comment:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - uses: jwalton/gh-find-current-pr@v1
         id: finder
         with:

.github/workflows/test.yml

@@ -3,12 +3,12 @@ on:
   pull_request:
   push:
     branches:
-      - master
+      - main
 
 jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - run: npm ci
       - run: npm run all