Support LSP style syntax

[Shougo]

Shougo/neosnippet.vim#412

https://github.com/Microsoft/language-server-protocol/blob/master/snippetSyntax.md

[Shougo]

Plus json snippet support.

https://github.com/neoclide/coc-tsserver/blob/master/snippets/typescript.json

[juanramirezc2]

@Shougo i'm glad that this plugin support LSP snippets completions, i have a question, now that neovim 0.5 is out. is this plugin safe to be use with deoplete, i gave it a try but i can see a [deoppet] message at the status line and no completion so far.

[Shougo]

Sorry. The plugin is not safe to use it yet.

The plugin supports deoplete completion, but it does not have useful features.

[Shougo]

https://github.com/rafamadriz/friendly-snippets

Another snippet repository.