Derive Hash for Location struct

[WillLillis]

First of all thanks so much for this project!

As part of some work in asm-lsp, I found it would be helpful if the Hash trait was derived on the Location struct, which I've done in this PR.

I looked through some of the other types defined in this project and saw that some could have Hash derived, but others could not as they contain a field of type serde_json::Value, which does not implement Hash. Is there any downside to deriving this trait when possible? I'd be happy to go through and add Hash derives as allowed on all structs in the crate if that would be helpful :)

[Marwes]

Only real downside is if the type later gets a field added which doesn't allow Hash, in which case the derive would have to be removed. For these three it seems reasonable to add them though.

[WillLillis]

Makes sense, thank you!