add build action

.github/workflows/build.yml

@@ -0,0 +1,17 @@
+name: Build LaTeX document
+on: [push]
+jobs:
+  build_latex:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Set up Git repository
+        uses: actions/checkout@v4
+      - name: Compile LaTeX document
+        uses: xu-cheng/latex-action@v3
+        with:
+          root_file: src/main.tex
+      - name: Upload PDF file
+        uses: actions/upload-artifact@v4
+        with:
+          name: PDF
+          path: src/main.pdf