ci: update MkDocs workflow to use requirements-docs.txt for dependencies

Co-authored-by: Copilot <copilot@github.com>

Author: marcialwushu

.github/workflows/docs-gh-pages.yml

@@ -6,6 +6,7 @@ on:
     paths:
       - "docs/**"
       - "mkdocs.yml"
+      - "requirements-docs.txt"
       - ".github/workflows/docs-gh-pages.yml"
   workflow_dispatch:
 
@@ -29,11 +30,12 @@ jobs:
         with:
           python-version: "3.12"
           cache: "pip"
+          cache-dependency-path: "requirements-docs.txt"
 
       - name: Install MkDocs
         run: |
           python -m pip install --upgrade pip
-          pip install mkdocs mkdocs-material
+          pip install -r requirements-docs.txt
 
       - name: Build docs
         run: mkdocs build --strict

requirements-docs.txt

@@ -0,0 +1,2 @@
+mkdocs
+mkdocs-material