POC: scientific notation

[Joshix-1]

Changes

Fixes #123

This builds upon #389 for correct rounding.

I'm not really happy with the code, but from my testing it works.

> e^(-2000) to 1 sn
approx. 3 × 10^-869
> e^(-2000) to 4 sn
approx. 2.577 × 10^-869
> 10 ^ -100 to 6 sn
1.00000 × 10^-100
> 10 ^ 100 to 4 sn
1.000 × 10^100

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Checklist

• I used LLMs or similar AI tools when creating this pull request