Add syntax highlighting for VimL snippet in README
@@ -274,7 +274,7 @@ The [gluon extension][] for Visual Studio Code provides syntax highlighting and
The gluon language server has been tested to work with https://github.com/autozimu/LanguageClient-neovim and https://github.com/prabirshrestha/vim-lsp.
#### Example configuration (autozimu/LanguageClient-neovim)
-```
+```vim
let g:LanguageClient_serverCommands = {
\ 'gluon': ['gluon_language-server'],
\ }
