Hot Reloading

[arctic-hen7]

Is your feature request related to a problem? Please describe.
It's about time Perseus supported reloading the server based on file changes.

Describe the solution you'd like
A new flag -w/--watch should be added to perseus serve and the other commands that will watch files for changes and reload the server. That shouldn't be too hard, though the next part will be reloading the browser automatically, which could either be done manually with a WebSocket server, or it could be done with browsersync (which other projects like Eleventy depend on, though it is JS some I'm a little apprehensive about that one).

Describe alternatives you've considered
People could just use a tool like entr, but not having this built in is quite silly I think, it's been requested since the earliest days of the project, and using entr and browsersync manually is way too complex (check out the website's scripts in bonnie.toml).

Additional context

• Add support for watching files with perseus build (No point to this.)
• Add support for watching files with perseus export
• Add support for watching files with perseus serve
• Add support for actively reloading the browser automatically (somehow...)

Also, quick note on HMR (Hot Module Reloading, keeping page state between reloads): I believe this would require significant integrations with Sycamore's state systems, so this is off the table for now, though I'm certainly not ruling it out as a longer-term feature.

[arctic-hen7]

This will be released for Perseus v0.3.1 (if all goes to plan).

[arctic-hen7]

Okay, I'll delegate automatic browser reloading to a future issue, and, as of v0.3.1, this is now live!