please add guidelines for preparing MWEs

I have submitted some bug reports before that were not actionable because there was no MWE attached, or the "M"WE was too large.

It would be great if the docs included some guidelines on **what** is considered a reasonable replication for a bug report from the perspective of package maintainers (eg a self-contained repo with a manifest, depending on whatever? a smaller repo with minimal dependencies? a maximum of N LOC, depending on base + stdlibs? the last, but not even stdlibs?), and, most importantly, **how** to achieve this.

I am finding the last point particularly tricky, as it frequently happens that issues just disappear as I pare down an example.

I am grateful for the Enzyme maintainers for all the great work and I realize that I have to do my own part when I open issues, but some guidance would really be helpful.