Add scope array literals to spec

[dkorpel]

Requested here: dlang/dmd#14562 (comment)

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[ntrel]

What about when the element type is not plain old data as mentioned in the changelog:
https://github.com/dlang/dmd/pull/14562/files#diff-a773cf7a39af2594f4e2e4f8aa41047d2b2f10a8558a5f0cb1c7d4c86f6d0304R23

[maxhaton]

What about when the element type is not plain old data as mentioned in the changelog: https://github.com/dlang/dmd/pull/14562/files#diff-a773cf7a39af2594f4e2e4f8aa41047d2b2f10a8558a5f0cb1c7d4c86f6d0304R23

As-if rule may be useful

[pbackus]

It is worth noting that this change (and others like it) may silently introduce memory corruption into any @trusted code that relied on the old behavior. For example, the following code is memory safe when compiled with DMD 2.100, but will be unsound when compiled with DMD 2.101:

@trusted int[] example()
{
    scope arr = [1, 2, 3];
    return arr;
}