Bun runtime support

[thescientist13]

Type of Change

Feature

Summary

Splitting of from #953 and based on some initial prototyping being conducted here, it seems like there is a very happy path towards basic Bun support for Greenwood.

What does that mean in practice? Effectively instead of using npm and node, levarge the equivalents in Bun

$ bun install
$ bun dev # maps to `greenwood develop`

Details

Some of the main considerations to account for as part of this work

1. Support custom imports - https://bun.sh/docs/runtime/plugins (align with migrate to register function for NodeJS custom imports (no more flag!) #1220)
2. Include a GitHub action to validate all test cases during Greenwood CI
3. Add documentation to the Greenwood website