feat: add bun runtime

[giovannisaraceno]

This pull request aims to add a new runtime based on Bun version 1.2.19 to the Apache OpenServerless project. The key changes include:

1 - Updating the Taskfile.yml to include the bun runtime in the list of supported runtimes.
2 - Adding a new Docker image definition for the bun:1.2.19 runtime, including the necessary environment variables and dependencies.
3 - Providing a custom compile script that handles the assembly and compilation of Bun-based actions.
4 - Updating the runtimes.json.tpl file to include the new bun:1.2.19 runtime definition, with the appropriate configuration settings.

[sciabarracom]

In order to test the runtime, can you please provide a couple of test actions (put them unnder tests/bun) including a single file and a multifile case and a non standard main, and build a public image in your github as ghcr.io/<user>/<runtime> so we can try see if the runtime works?