add vim-lsp

Vim.md

@@ -1,7 +1,38 @@
 There are several implementations of language server protocol (client side) in Vim.
 
+First, make sure you have `ccls` built following [[Getting Started]] and added to `$PATH` (e.g. via soft link).
+
 ## vim-lsp
 
+Install [vim-lsp](https://github.com/prabirshrestha/vim-lsp) following its README.
+
+Register ccls by adding the following into your `~/.vimrc` or `~/.vim/vimrc`:
+
+```vim
+" Register ccls C++ lanuage server.
+if executable('ccls')
+   au User lsp_setup call lsp#register_server({
+      \ 'name': 'ccls',
+      \ 'cmd': {server_info->['ccls']},
+      \ 'root_uri': {server_info->lsp#utils#path_to_uri(lsp#utils#find_nearest_parent_file_directory(lsp#utils#get_buffer_path(), 'compile_commands.json'))},
+      \ 'initialization_options': { 'cacheDirectory': '/tmp/ccls/cache' },
+      \ 'whitelist': ['c', 'cpp', 'objc', 'objcpp', 'cc'],
+      \ })
+endif
+```
+
+Note you may want to customize `cacheDirectory` and `whitelist` of C/C++/... file suffixes to your taste.
+
+Next, set up key bindings by adding the following to your `~/.vimrc` or `~/.vim/vimrc`:
+
+```vim
+" Key bindings for vim-lsp.
+nn <silent> <M-d> :LspDefinition<cr>
+nn <silent> <M-r> :LspReferences<cr>
+nn <f2> :LspRename<cr>
+```
+
+Now it's good to go! Navigate to a C/C++/... project and test. Make sure you have [compilation database](https://github.com/MaskRay/ccls/wiki/compile_commands.json) in that project.
 
 
 ## LanguageClient-neovim