Upgrade to Serde 1.0 and languageserver-types 0.50

[strager]

Upgrade RustLSP to the Serde 1.0.0 and languageserver-types 0.50.0. Using a stable version of Serde and a recent version of languageserver-types will let people more easily use rustdt-json_rpc.

This pull request requires RustDT/rustdt-json_rpc#2.

These commits address RustDT/rustdt-json_rpc#1.

Note to maintainers: I strongly prefer rebasing or merging (and not squashing) to preserve history.

[bruno-medeiros]

Are you using RustLSP or planning to? I'm not sure it's worthwhile to continue developing this project, it was never used upstream in any significant project, as far as I know.

[strager]

Yes, I am using RustLSP for a new project.

[bruno-medeiros]

Hum, I see. Well, I am going to have a break between my contract jobs later this year. I'll have some free time and I wanna catch up on my Rust, so I'll look into this project then, and see if it's worth revisiting.