This PR adds support for [Gleam](https://gleam.run/).

<img width="1320" alt="Screenshot 2024-01-25 at 6 39 18 PM"
src="https://github.com/zed-industries/zed/assets/1486634/7891b6e9-d7dc-46a0-b7c5-8aa7854c1f35">

<img width="757" alt="Screenshot 2024-01-25 at 6 39 37 PM"
src="https://github.com/zed-industries/zed/assets/1486634/f7ce6b3f-6175-45cb-8547-cfd286d918c6">

<img width="694" alt="Screenshot 2024-01-25 at 6 39 55 PM"
src="https://github.com/zed-industries/zed/assets/1486634/b0838027-c377-47e6-bdd1-bdc9b67a8672">

There are still some areas of improvement, like extending what
constructs we support in the outline view, but this is a good start.

Release Notes:

- Added Gleam support
([#5162](https://github.com/zed-industries/zed/issues/5162)).