Implement a file watcher

[aslowwriter]

This one is really for the future, but at some point I want to implement a file watcher, just like zola serve has in some capacity so that snakedown can regenerate the docs when there is change in the file, which then in combination with something like zola serve should enable live editing of the docstrings with a preview. This is a big goal, and whether it is feasable remains to be seen. This issue for now is mostly for discussion and reminding myself of it.

[aslowwriter]

Note to self: There is a case to be made that because this will require multiple services (e.g. at least snakedown + your SSG of choice) having th watching built into the binary is actualy not the way to go. It might instead be better to investigate a good recomendation for a local orchestrator and provide some setup for that instead.

Some options to look into:

• https://github.com/shakacode/steward
• https://mise.jdx.dev/tasks/architecture.html
• https://just.systems/man/en/parallelism.html
• https://docs.docker.com/compose/