Update actions since we renamed our main branch.

Author: FredTingaud

.github/workflows/action.yml

@@ -3,7 +3,7 @@ name: Check Markdown links
 on: 
   push:
     branches:
-    - master
+    - main
   schedule:
   # runs every monday at 9 am
   - cron: "0 9 * * 1"
@@ -12,7 +12,7 @@ jobs:
   markdown-link-check:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v2
     - uses: gaurav-nelson/github-action-markdown-link-check@v1
       with:
         use-quiet-mode: 'yes'