readBigUInt64BE() and similar methods are missing

[nazar-pc]

Essentially getting this in Browserify build:

TypeError: Buffer.from(...).readBigUInt64BE is not a function

[feross]

According to Node docs this was added in Node 12.0.0 so it makes sense that it's missing from here.

[nazar-pc]

Yes, but v12 is out for a while now, so I think it is time to consider implementing new methods.

[feross]

I'd love to do it, but I'm very time-constrained at the moment. PR welcome, from you or anyone else!

[fanatid]

Node.js internally uses BigInt constructor, if this package will start use it... should this methods be available if BigInt is not available in environment?
I'm not familiar too much with bundling systems, can usage of BigInt cause any issues with it?

[feross]

@fanatid I like this approach. It should be possible to detect the existence of BigInt and make the methods throw if it's not available.

BigInt availability is already quite good (70%) and only improving. And this is certainly better than not supporting it at all. Want to send a PR?

[fanatid]

Yep, I'd like to try, but little busy now. If I'll start work on this I'll left comment (probably on next week).

[fanatid]

Just checked how this implemented in node. I think better finish #217 first. @feross are you ok with this?
For reference, PR in node: nodejs/node#19691

[feross]

Yep, feel free to tackle this in any order your prefer. Finishing #217 first sounds good. Thanks for all your help, @fanatid.

[feross]

Released as 6.0.0