Replace pin-project with pin-project-lite

[ravenclaw900]

pin-project-lite is a version of pin-project written with declarative macros instead of proc macros. It has the same feature set, but removes all proc macro related dependencies. It is used by tokio and hyper as an alternative to pin-project.

After reading #3, I saw that pin-project-lite was offered as an option there, but not used. I think that since both hyper and tokio now use pin-project-lite, it should be safe to switch over, and it will clean up the dependency tree for projects using this crate.

[de-vri-es]

Oops, I somehow missed that you made a PR for it instead of an issue. Let me do some fiddling with git to get your commit in the main branch.

[de-vri-es]

Merged and release as v0.11.1 (although not in that order 😄 )

tungstenite still pulls in thiserror which pulls in proc-macro crates, but atleast we're not pulling them in here anymore!

Thanks for the PR!