ci(CompatHelper): checkout the repository (#542)

Without checking out the repository, trying `readdir("lib")` will
throw an error. Checking out the repository first fixes the
presently broken CompatHelper action.

Author: thazhemadam

.github/workflows/CompatHelper.yml

@@ -15,11 +15,14 @@ jobs:
         julia-arch: [x86]
         os: [ubuntu-latest]
     steps:
+      - uses: actions/checkout@v4
       - uses: julia-actions/setup-julia@latest
         with:
           version: ${{ matrix.julia-version }}
+
       - name: Pkg.add("CompatHelper")
         run: julia -e 'using Pkg; Pkg.add("CompatHelper")'
+
       - name: CompatHelper.main()
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}