feat(cli): ags run naive --watch mode

[Aetherall]

Hi !

Most of the code and ideas are retrieved from #634

With the difference of using esbuild watch mode in an attempt to delegate cache invalidation to the builder.

First time writing go, so please review with caution :)

[Aetherall]

Hi @Aylur, Thanks a lot for your work on ags and astal :)

Maybe this PR can help with the watch mode request ?
Have a great day !

[j4ger]

While this is pending for merge, I'm using this workaround to get working live reload:
(This is in Justfile syntax, but it can be used in a bash script with minimal changes)

run:
    @while true; do \
        echo "Starting the bar..."; \
        ags run --gtk4 . & \
        echo "Bar started, waiting for file changes..."; \
        inotifywait -q -r -e modify,move,create,delete .; \
        echo "File change detected. Killing bar"; \
        pkill ags; \
        pkill gjs; \
    done