Actions: Re-unify master and non-master workflow

Author: iBug

.github/workflows/deploy.yaml renamed to .github/workflows/build.yaml

@@ -1,20 +1,11 @@
 name: build
 
 on:
-  push:
-    branches:
-      - "master"
-
-permissions:
-  contents: write
-  pages: write
-  id-token: write
+  - pull_request
+  - push
 
 jobs:
   build:
-    environment:
-      name: github-pages
-      url: ${{ steps.deployment.outputs.page_url }}
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -53,6 +44,7 @@ jobs:
           globs: |
             docs/**/*.md
             README.md
+
       - name: Stop and report errors
         run: |
           git add -A
@@ -66,18 +58,25 @@ jobs:
           mkdocs -v build
           : > site/.nojekyll
           echo -n '201.ustclug.org' > site/CNAME
+
       - name: Upload artifact
-        if: github.ref == 'refs/heads/master'
         uses: actions/upload-pages-artifact@v3
         with:
           path: site
+
+  deploy:
+    needs: build
+    if: github.ref == 'refs/heads/master'
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    steps:
       - name: Deploy to GitHub Pages
-        if: github.ref == 'refs/heads/master'
         id: deployment
         uses: actions/deploy-pages@v4
 
       - name: Push site to gh-pages branch
-        if: github.ref == 'refs/heads/master'
         run: |
           CINFO="$(git log -1 --pretty="%an: [%h] %s")"
           git clone --depth=1 --branch=gh-pages --single-branch --no-checkout \