Slices

Support slices like in Go/Zig/D/...

Current syntax that most use is something like;
```C
array := [1, 2, 3, 5]
A.x = array[0..] // from 0 to the end
A.x = array[..5] // from 0 to 5 (including the '5')
```
Maybe we would also want support for things like `.length` on the arrays?