Update checkout action (#23)

Fixes node deprecations

Author: sciencewhiz

.github/workflows/main.yml

@@ -7,7 +7,7 @@ jobs:
     name: Build
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - run: make update
       - run: make build
       - run: |