feat(layout): add nbLtr and nbRtl directives

[katebatura]

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• I read and followed the CONTRIBUTING.md guide.
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Short description of what this resolves:

Adds two structural directives which display the template content depending on layout direction.
*nbLtr displays the content when layout direction is ltr.
*nbRtl displays the content when layout direction is rtl.

How to use:

<div *nbLtr>This displays when layout direction is ltr</div>

<div *nbRtl>This displays when layout direction is rtl</div>