shinyngs feature/observation matrix validation module

[pinin4fjords]

The wrapped script in shinyngs reuses a bunch of package code to ensure consistency with the various components of feature/ observation matrices (FOM, e.g. gene/ sample/ matrix) and a set of contrast definitions. I think it might be handy as an input checker for workflows such as differential abundance, but even if not it may be useful elsewhere.

PR checklist

Closes #2390

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[pinin4fjords]

@nf-core-bot fix linting

[SPPearce]

Looks good to me.

[pinin4fjords]

Thanks for review @SPPearce