Make re2 optional

[JamieMagee]

Right now re2 is always imported. Regardless of if it's used or not:

node-docker-reference/lib/parsers.js

Line 3 in 957b11b

const RE2 = require('re2');

re2 is precompiled and not available for all architectures. node-docker-reference should attempt to load it, but fall back to RegExp if re2 is not available. For example, here's how it's handled in Renovate:

https://github.com/renovatebot/renovate/blob/48af4012e6d0b4d90a9aeb4df1471f452b677cd8/lib/util/regex.ts#L11-L20

[adammfrank]

Yes please, this is broken for ARM Macs.

[adammfrank]

@JamieMagee I implemented your suggestion here

https://github.com/swimlane/node-docker-reference