Consider making terms in getting started headings

[greyscaled]

Context

Getting Started page: https://langium.org/docs/getting-started/

Description

Hello 👋🏻 ,

I'm digging into Langium (it's awesome). Just wanted to drop a minor suggestion.

It might be nice-to-have if the following important terms were sub-headings, so that they could be linked to elsewhere in the documentation and just stand out more:

I'm happy to contribute this if need be, but thought I'd open an issue before to see if it's worthwhile.