fix: Update env.exit_code to outputs.exit_code

The previous expression always gives `false`.
Both `env.exit_code` and `env.lychee_exit_code` are `null`, probably since the docker→composite refactor #128. When GitHub evaluates the expression, it finds the types do not match, and coerces them to number, namely, `null` → `0`.

See [Evaluate expressions in workflows and actions - GitHub Docs](https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/evaluate-expressions-in-workflows-and-actions#operators).

Relates to #253.

.github/workflows/links.yml

@@ -15,6 +15,7 @@ jobs:
       - uses: actions/checkout@v4
 
       - name: Link Checker
+        id: lychee
         uses: ./ # Uses an action in the root directory
         with:
           args: --user-agent "Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:59.0) Gecko/20100101 Firefox/59.0" --verbose --exclude spinroot.com --no-progress './**/*.md' './**/*.html' './**/*.rst'
@@ -23,7 +24,7 @@ jobs:
           GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
 
       - name: Create Issue From File
-        if: env.exit_code != 0
+        if: ${{ steps.lychee.outputs.exit_code }} != 0
         uses: peter-evans/create-issue-from-file@v5
         with:
           title: Link Checker Report

README.md

@@ -37,7 +37,7 @@ jobs:
         uses: lycheeverse/lychee-action@v2
 
       - name: Create Issue From File
-        if: env.exit_code != 0
+        if: ${{ steps.lychee.outputs.exit_code }} != 0
         uses: peter-evans/create-issue-from-file@v5
         with:
           title: Link Checker Report