Add ⏨ as exponent notation for floats.

[clsn]

To address #1347 in case anyone eventually cares.

[zoffixznet]

👎 from me on this.

I doubt many people will use this and it's even in the same token that has the U+2212 minus, which in the past caused tons of bugs, that is still buggy in cases, and that I've never seen anyone use.

This falls squarely into "you think this is cute now" category that we'd be regretting in the future.

[zoffixznet]

which in the past caused tons of bugs

Already spotted one bug were this PR accepted: &val (and subsequently Str.Numeric) won't know how to handle this syntax and would need fixing. I suspect sprintf won't either and that lives in nqp.

[AlexDaniel]

Yeah we'll have to put that into the drawer for now. Who knows, maybe we'll get back to it later. In any case, it's now listed on the wiki and I even added a link to this PR. Further discussion is welcome but this won't be added in the very near future.