BigInt::ToWords docs not consistent with implementation

[adrian-gierakowski]

first 2 args are swapped

the docs:

node-addon-api/doc/bigint.md

Line 82 in cdb6625

void Napi::BigInt::ToWords(size_t* word_count, int* sign_bit, uint64_t* words);

implementation:

node-addon-api/napi.h

Line 388 in 9c9accf

void ToWords(int* sign_bit, size_t* word_count, uint64_t* words);

[NickNaso]

@adrian-gierakowski Thanks for your feedback. I made a PR that fix the inconsistency with the documentation.

[NickNaso]

I'm closing the issue because #748 has been merged.