feature request: ability to set include paths via initializationParams

[segoon]

I use neovim and protols. Sometimes it's required to set extra include paths. Current method of protols argv is not dynamically configurable for neovim. Neovim expects cmd (and args) to be static, but it allows one to change initializationParams via before_init callback.

It would be VERY handy to be able to set include paths via initializationParams.

[asharkhan3101]

Can you try building from #91 and report if this works. I will take a look at it during weekend if the above PR doesn't works.