dot methods completion

[xgdgsc]

Fixes https://github.com/julia-vscode/LanguageServer.jl/issues/979 .

Updates https://github.com/julia-vscode/LanguageServer.jl/pull/980.
completes

dframea = DataFrame()
dframea.

show list, then select append! to

append!(dframea,)

A few issues remain:

• [x] cannot search the list
• [ ] the change in line 16 needed to show the list, I don' t know if it's right to change this.
• [ ] whether it' s ok to use dot as trigger.
• [x] Some types don' t work, like Vector (Works in REPL runtime by https://github.com/julia-vscode/julia-vscode/pull/3240 )
• [ ] move cursor to middle of ",<CURSOR>)"
• [x] Would it be better to call methodswith in REPL mode?

I remember Golang does this in IDE. I think it' s a convenient way for people coming from OOP to find the relevant methods and gradually adapt to the Julian way. I' m looking for suggestions and opinions.