[FEATURE]: Augment custom tools with an optional `install` hook

[DamianB-BitFlipper]

Feature hasn't been suggested before.

• [x] I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

When writing a custom tool that invokes another programming language (ie python), unless the tool is trivial, often times extra python libraries are needed.

For one tool, I had to manually create a venv and then use that in the Bun.$ command. I was thinking it would be greatly beneficial to have the installation happen automatically, making custom tools much more portable and shareable.

My idea is to have the tool optionally provide an install function which gets called and installs whatever is needed in the .../plugin/<tool_name> directory. If this directory already exists, the install is a no-op.

I'd be happy to implement this feature since it is one I found the need for.