* update nvim version to 0.11.0
* replace deprecated nvim_err_write/nvim_err_writeln call
* replace deprecated func for diagnostic and lsp
* use vim.hl instead
* use new way to define diagnostic signs
1. Add new command `CopyPath`
2. Revise command `JSONFormat`: implemented using the nvim lua interface
and fix a few issues. The previous implementation is removed.