[Feature Request] fire autocmd on end of `makeState`

[kuuote]

Description

I want to running makeState at background. but it was asynchronous process.
Therefore I think it solved if event fired at end of makeState.

Idea

Implements roughly proposal to https://github.com/kuuote/dpp.vim/tree/feat-dppmakestatedone
and assumed configuration is following code.

" from help
if dpp#min#load_state(s:dpp_base)
  execute 'set runtimepath^=' .. s:denops_src
  autocmd User DenopsReady
  \ call dpp#make_state(s:dpp_base, '{your TypeScript file path}')
endif

" and auto exit
autocmd User DppMakeStateDone * quit!

[Shougo]

I have added dpp:makeStatePost autocmd.