Add regression tests for lua support

Change Dockerfile to install lua, luajit and love and also to install
nodejs 12 needed to build the lua debug adapter. Create the
love-headless test in support/test/lua to test love without an x server.

.github/workflows/build.yaml

@@ -86,7 +86,7 @@ jobs:
     - run: |
         brew update-reset
         brew doctor || true
-        for p in macvim tcl-tk llvm; do
+        for p in macvim tcl-tk llvm lua luajit love; do
           brew install $p
           brew outdated $p || brew upgrade $p
         done