Reference Persistent and Weak shortcuts incorrect in documentation

[DuBistKomisch]

Hi, just trying converting some code from nan to n-api using this library and the docs have been pretty good except for this.

Napi::FunctionReference::Persistent is listed here: https://github.com/nodejs/node-addon-api/blob/44f0695533327a12548a5015c444a3a5d731bb5c/doc/function_reference.md#persistent

However the actual method is Napi::Persistent overloaded to take a Napi::Function as seen in the source code here:

node-addon-api/napi.h

Line 1130 in 44f0695

FunctionReference Persistent(Function value);

The mistake seems to have been introduced a few months ago in a docs tidy up: fc11c94#diff-9562158c05ed3ee744cdc12bad121e87L39

The same mistake seems to exist for all Persistent and Weak across Reference and its subclasses.

This could be part of the confusion in #392.

[mhdawson]

@DuBistKomisch thanks for the report. Do you want to submit a PR to fix this up?

[DuBistKomisch]

@mhdawson sure

[mhdawson]

Closing this issue as a PR to fix has landed (Thanks @DuBistKomisch).