I have implemented DIP1039 - Static Arrays with Inferred Length

[xoxorwr]

This is something I miss a lot whenever I come back to D from 
other languages.

There's always been that friction when dealing static arrays 
that's very annoying

- you either have to manually count elements
- or have to tap into phobos `auto arr = [1, 2, 3].staticArray;`

But no more! PR is ready for review: 
https://github.com/dlang/dmd/pull/22623

There was a DIP for it, but honestly, the review process is way 
too stalled and convoluted, it's become over engineered for what 
is ultimately a minimal diff for a minimal feature.