feat(layout): add mirror nerps (Beethoven-n)

[Beethoven-n]

Description

Added a mirrored nerps keyboard layout.

Checks

• Check if any open issues are related to this PR; if so, be sure to tag them below.
  technically related to Add "layout mirror" funbox #5573 but not by much
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Closes #

someone asked me try this and i found it was really easy to add in once i set up a dev environment lol

[Beethoven-n]

forgot to give an ansi-style screenshot lol

[Beethoven-n]

fuck, the commit doesn't match my username exactly