build instructions and removal of built files (and gh action)

.github/workflows/build.yml

@@ -0,0 +1,49 @@
+name: Build
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v4
+    
+    - name: Set up Python
+      uses: actions/setup-python@v5
+      with:
+        python-version: '3.x'
+    
+    - name: Install LaTeXML and dependencies
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y latexml
+        sudo apt-get install -y texlive-latex-extra
+    
+    - name: Create Python virtual environment
+      run: |
+        python3 -m venv venv
+        venv/bin/pip install --upgrade pip
+        venv/bin/pip install beautifulsoup4
+    
+    - name: Create export directory
+      run: mkdir -p export
+    
+    - name: Build with LaTeXML
+      run: latexmlc --destination=export/index.html pghrt
+    
+    - name: Run soup.py post-processing
+      run: venv/bin/python soup.py
+    
+    - name: Upload export artifacts
+      uses: actions/upload-artifact@v4
+      with:
+        name: latexml-export
+        path: export/
+        retention-days: 90