Provide guidance for installing LSPs

[ItsHarper]

This will often apply to the languages that have built-in support upstream or whose extensions attempt to download the LSP using NPM. Since Zedless doesn't have node integrated or do auto-downloads like Zed does, these LSPs will need to be manually downloaded and installed. I think we should guide the user to do so.

[ItsHarper]

This is basically the opposite of the logic used for https://github.com/zedless-editor/zedless/pull/29, so this would probably be best as a setting. I think the default should be to warn users, so that they're clued into why they're not getting LSP features.

Alternatively, we could keep the no-warnings status quo, but make it so that clicking on a server that's stopped because it's missing will inform you that it's missing, and what you can do about it.

[max-privatevoid]

Yeah, I thought about adding an extra color or a warning icon or something in the LSP menu. Unsure about the warning notification. I'd prefer to not have it, so as to not bug the user. It might be enough to just show the warning inside the LSP menu.

[ItsHarper]

Yeah I don't think we need a pop-up notification, though I think there should be a warning indicator of some sort at the menu icon, not just once you click it.