Deprecate `flow` linter

Hi, I am from the Flow team and I am contemplating deprecating our non-LSP APIs. I wanted to discuss deprecating the `flow` ALE linter in favor of the `flow-language-server` linter.

I have to admit that I'm not a regular vim user, so my experience with ALE is very limited. But as far as I can tell, `flow-language-server` is a superset of `flow` since both handle diagnostics.

I think it'd be great if the two linters merged, so that `flow` used the LSP (perhaps only for newer Flow versions?) and `flow-language-server` got deprecated. `flow` is the better, more consistent name IMO.

If there are any issues with our LSP implementation that make people prefer the `flow` linter, I'd like to resolve those ASAP. The LSP is our primary API going forward.