Batch 'addArticle's

[ISNIT0]

The majority of CPU time in CPP (18.8%) when using node-libzim seems to be calls to v8::internal::Builtin_HandleApiCall.

I'm not sure how much it would improve the performance, but we could try creating an addArticles method in CPP and automatically batch the adding on the JS side.
This would keep the same simple API, but potentially improve performance

[kelson42]

@ISNIT0 Have a look to nodejs/node#17996, might be completely insignificant.

[ISNIT0]

@kelson42 in that issue, the total percentage was 0.1%, in our case it's 18.8%, so I think it matters much more for us 😀

[kelson42]

@audiodude Do you have some kind of insight on this. Actually I had forgotten about this issue, and that might be a good way to speed-up MWoffliner.

[audiodude]

I'm not sure. I think mwoffliner will continue to be I/O bound because of all the network calls.