add Github action to compile

Author: Vladimir Kotal

.github/workflows/pdfs.yml

@@ -0,0 +1,26 @@
+name: Compile
+on:
+  push:
+    branches:
+    - master
+    paths:
+    - *.tex
+    - *.m4
+    - *.sty
+    - Makefile
+    - .github/workflows/pdfs.yml
+    - img/**
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Update the system
+      run: sudo apt-get -qq update
+    - name: Install pre-requisites for LaTeX
+      sudo apt-get install -y --no-install-recommends texlive-fonts-recommended texlive-latex-extra texlive-fonts-extra dvipng texlive-latex-recommended texlive-pstricks aspell aspell-en
+    - name: Run spellcheck
+      run: make spellcheck
+    - name: Compile first phase
+      run: make slides notes
+    - name: Compile second phase to get table of contents
+      run: make slides notes