Port Lychee link checker to user documentation (#531)

.github/workflows/check-links.yaml

@@ -1,16 +1,37 @@
-name: Check Markdown links
+name: Check external href links in the documentation
 
 on:
+  push:
+    paths:
+      - '.github/workflows/check-links.yml'
+      - '.lycheeignore'
+      - 'lychee.toml'
+      - '**/*.md'
+  schedule:
+    # Run on the first of each month at 9:00 AM (See https://pubs.opengroup.org/onlinepubs/9699919799/utilities/crontab.html#tag_20_25_07)
+    - cron: "0 9 1 * *"
   workflow_dispatch:
 
+concurrency:
+  group: "${{ github.workflow }}-${{ github.head_ref || github.ref }}"
+  cancel-in-progress: true
+
 jobs:
-  markdown-link-check:
+  lychee:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: gaurav-nelson/github-action-markdown-link-check@v1
+      - uses: actions/checkout@v4
+        with:
+          show-progress: 'false'
+      - name: Restore lychee cache
+        uses: actions/cache@v4
+        with:
+          path: .lycheecache
+          key: cache-lychee-${{ github.sha }}
+          restore-keys: cache-lychee-
+      - name: Link Checker
+        id: lychee
+        uses: lycheeverse/[email protected]
         with:
-          use-quiet-mode: 'yes'
-          use-verbose-mode: 'no'
-          config-file: 'mlc_config.json'
-          folder-path: 'en'
+          fail: true
+          args: --accept '200,201,202,203,204,403,429,500' --max-concurrency 1 --cache --no-progress --exclude-all-private './**/*.md'

.lycheeignore

@@ -0,0 +1,16 @@
+https://arxiv.org/
+https://chrome.google.com/
+https://contribute.jabref.org/
+https://donations.jabref.org/
+https://pubs.acs.org/
+https://scholar.archive.org/
+https://web.archive.org/
+https://www.researchgate.net/privacy-policy
+https://www.sciencedirect.com/
+
+https://github.com/koppor/jabref/issue
+https://github.com/koppor/jabref/pull
+https://github.com/JabRef/jabref/issue
+https://github.com/JabRef/jabref/pull
+
+0005-example.md