Consider making re2 an optional dependency?

[aldenquimby]

Thank you for this library! My team recently started using it, and it's great.

We hit issues initially with re2 that took us a bit to work around. re2 causes difficulties for many build systems, e.g evanw/esbuild#1051

Would you be open to making this an optional peer? That way anyone that wants it can install it, but if it's problematic for a build and you aren't worried about backtracking, then it doesn't need to be installed.

Here is an example of what the implementation could look like, from a lib getting 100k+ downloads per week: https://github.com/spamscanner/url-regex-safe/blob/6c1e2c3b5557709633a2cc971d599469ea395061/src/index.js#L37-L49

[baptistejamin]

We are opened to contributions :)

[aldenquimby]

@baptistejamin ok great! Here you go #34