[Issue 20272] Add standard section "Limitations" to ddoc

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20272

--- Comment #2 from Berni <dlang at croco-puzzle.com> ---
Similarly, but not identically. See discussion of
https://github.com/dlang/phobos/pull/7199

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