Add Support for GDScript Syntax Highlighting

[ghost]

GDScript is the official scripting language of the promising Godot game engine.

It is rising in popularity and becoming a force on its own for game development.

Supporting it for syntax highlighting makes total sense imo.

[marijnh]

We're not adding more language modes to the main distribution. The way to work with a new language is to write the mode as a separate module, and possibly publish that to NPM so that others can benefit from it.

[AsixJin]

How would I go about making a language mode into a module so someone like the people at Boostsnotes could implement it into their projects?

[adrianheine]

We usually reference the elexir mode as an example.