Updated docs

[don-tre]

added method call with named argument
added fluent method call

[don-tre]

@TomasVotruba Hello! You have very good repo, it helped me very well.

I got a little bit stuck during investigation fluent method calls, maybe this doc addition would be useful for some one.

[TomasVotruba]

Hi, thanks for you contribution. I'm glad you find it useful 👍

To add a snippet, just add code here and regenerate the file:
https://github.com/rectorphp/php-parser-nodes-docs/tree/master/snippet

[TomasVotruba]

I had to update the core code, as there was a layer of 2-years dust :)

While at it, I've cherry picked your snippet and added it to save you the hustle:
#4

Thanks 👍