Replace hard coded max char count with variable

This allows us more flexibility to adjust the max length in the future
without doing a find-and-replace accross the workflow file

Author: rmainwork

.github/workflows/build-pr-preview.yml

@@ -337,23 +337,23 @@ jobs:
       # artifacts and just link to that instead
       - name: Upload lychee report to GitHub artifacts
         id: upload-artifact
-        if: steps.lychee.outputs.exit_code != 0 && steps.char-count.outputs.size >= 65536
+        if: steps.lychee.outputs.exit_code != 0 && steps.char-count.outputs.size >= vars.BROKEN_LINK_REPORT_CHAR_MAX
         uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # 4.6.2
         with:
           path: ./lychee/out.md
           name: Link Checker Report
 
       - name: Comment on PR with link to full link checker report
-        if: steps.lychee.outputs.exit_code != 0 && steps.char-count.outputs.size >= 65536
+        if: steps.lychee.outputs.exit_code != 0 && steps.char-count.outputs.size >= vars.BROKEN_LINK_REPORT_CHAR_MAX
         uses: marocchino/sticky-pull-request-comment@52423e01640425a022ef5fd42c6fb5f633a02728 # v2.9.1
         with:
           header: Link Checker Report
           message: |
             ## Broken Link Checker
-            Report exceeds max length of 65536 characters. See ${{steps.upload-artifact.outputs.artifact-url}} for full report
+            Report exceeds max length of ${{vars.BROKEN_LINK_REPORT_CHAR_MAX}} characters. See ${{steps.upload-artifact.outputs.artifact-url}} for full report
 
       - name: Comment on PR with link checker report
-        if: steps.lychee.outputs.exit_code != 0 && steps.char-count.outputs.size < 65536
+        if: steps.lychee.outputs.exit_code != 0 && steps.char-count.outputs.size < vars.BROKEN_LINK_REPORT_CHAR_MAX
         uses: marocchino/sticky-pull-request-comment@52423e01640425a022ef5fd42c6fb5f633a02728 # v2.9.1
         with:
           header: Link Checker Report