Modularizes gloo

[xfbs]

This turns the individual subcrates into optional features. By default, all features are enabled, to ensure this change is not a breaking change. But if needed, default features can be turned off and only the modules needed enabled.

[ranile]

Thanks for the PR! I have to ask: why make this change? Depending upon the individual crates is always an option

[xfbs]

Hey!

I can try to explain:

Basically, right now with gloo you either get everything or nothing (you have to manually import crates). Often times it would be convenient to import gloo and have something in-between. For example get gloo with the net, timers and events features. Somewhat like tokio (where you would enable fs and sync features).

Especially in WASM where you are trying to get small binaries (because they load through the browser) you often don't want to blindly import everything (although, to be fair, wasm-opt seems to be doing a really good job of throwing stuff that isn't used out).

If you think this does not make sense, feel free to disregard it. I would like for gloo to be modular like this, but it is not really "necessary", just a way for lazy people like me to use gloo without needing to add many manual imports!

Cheers,
-Patrick

[ranile]

Sounds reasonable