Added test CI action

.github/workflows/publish.yaml

@@ -1,6 +1,9 @@
 name: Publish PDF
 
-on: push
+on:
+  push:
+    branches:
+      - main
 
 jobs:
   publish:

.github/workflows/test.yaml

@@ -0,0 +1,25 @@
+name: Test PDF
+
+on: push
+
+jobs:
+  compile:
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+      - name: Extract branch name
+        shell: bash
+        run: echo "branch=${GITHUB_HEAD_REF:-${GITHUB_REF#refs/heads/}}" >> $GITHUB_OUTPUT
+        id: extract_branch
+      - name: Setup tectonic
+        run: | 
+          apt -y install curl
+          curl --proto '=https' --tlsv1.2 -fsSL https://drop-sh.fullyjustified.net |sh
+      - name: Restore cache
+        id: cache-restore
+        uses: actions/cache/restore@v4
+        with:
+          path: ~/.cache/Tectonic
+          key: ${{ runner.os }}-tectonic-
+      - name: Compile latex
+        run: ./tectonic book.tex