add Linkspector

.github/workflows/links.yml

@@ -0,0 +1,14 @@
+name: Linkspector
+on: [pull_request]
+jobs:
+  check-links:
+    name: runner / linkspector
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Run linkspector
+        uses: umbrelladocs/action-linkspector@v1
+        with:
+          github_token: ${{ secrets.github_token }}
+          reporter: github-pr-review
+          fail_level: any

book/intro.md

@@ -16,4 +16,4 @@ There are several "parts" to the manual:
 - The **Features** part describes a suite of tools that are useful for teachers, many of which are developed by TeachBooks contributors specifically for use in education. Many of these tools are illustrated in the **Examples**.
 - A few special tools are included in the **Editing Tools** that are useful when writing content.
 
-See the final chapters of this book (under **Miscellaneous**) for additional information about References, Credits, etc.
+See the final chapters of this book (under **Miscellaneous**) for additional information about References, Credits, etc.