lang/lua: improve moonscript & love2D support

- Fix moonscript-mode not highlighting/treating single-quoted strings as
  strings
- Fontify interpolated expressions in moonscript-mode strings (PR
  upstream?)
- Fix +lua-love-mode project detection
- Fix +lua/run-love-game love project root resolution

modules/lang/lua/autoload/moonscript.el

@@ -0,0 +1,16 @@
+;;; lang/lua/autoload/moonscript.el -*- lexical-binding: t; -*-
+;;;###if (featurep! +moonscript)
+
+;;;###autoload
+(defun +lua|moonscript-fix-single-quotes ()
+  "Single-quoted strings aren't treated as strings."
+  ;; (modify-syntax-entry ?\" "\"" moonscript-mode-syntax-table)
+  (modify-syntax-entry ?\' "\"" moonscript-mode-syntax-table))
+
+;;;###autoload
+(defun +lua|moonscript-fontify-interpolation ()
+  "Highlight interpolated expressions in moonscript strings."
+  (font-lock-add-keywords
+   nil '(("#{\\([^}]+\\)}"
+          (0 font-lock-preprocessor-face t)
+          (1 nil t)))))