Fix link checker accepted status codes and base URL (#736)

Accept normal 2xx responses and resolve root-relative links against the deployed site.

Co-authored-by: Matt McKay <mmcky@users.noreply.github.com>

Author: Zhengyizhe0209-arch

.github/workflows/linkcheck.yml

@@ -21,11 +21,11 @@ jobs:
         uses: lycheeverse/lychee-action@v2
         with:
           fail: false
-          args: --accept 403,503 *.html
+          args: --accept 200..=299,403,503 --base-url https://intro.quantecon.org *.html
       - name: Create Issue From File
         if: steps.lychee.outputs.exit_code != 0
         uses: peter-evans/create-issue-from-file@v6
         with:
           title: Link Checker Report
           content-filepath: ./lychee/out.md
-          labels: report, automated issue, linkchecker
+          labels: report, automated issue, linkchecker