Clean up lua docs scripts

- ldoc is now a git submodule
- ldoc can be installed using scripts/install.{sh,ps1}
- lua docs can be build using scripts/build.{sh,ps1}
- all lua docs-related files now reside inside of the docs folder

docs/scripts/build.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)"
+cd "$DIR/.."
+
+ldoc_path=./lua_modules/bin/ldoc
+
+if [[ ! -x "$ldoc_path" ]]; then
+  echo "ldoc not found; please run docs/scripts/install.sh"
+  exit 1
+fi
+
+rm -rf ./html
+mkdir ./html
+
+cp -r ./js/. ./html
+cp -r ./css/. ./html
+
+"$ldoc_path" .