Semantic tokens highlighting is added now
* same configurations as VSCode extension, `rust-analyzer.server.path`, `rust-analyzer.cargo.features` etc.
* same commands too, `rust-analyzer.analyzerStatus`, `rust-analyzer.ssr` etc.
* inlay hints for variables and method chaining, _Neovim Only_
- * semantic highlighting is not implemented yet
Note: for code actions, use `coc-codeaction-cursor` and `coc-codeaction-selected`; `coc-codeaction` and `coc-codeaction-line` are unlikely to be useful.