gh-37315: Reference manual: Show package list by category (math/front-end/other)
    
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Likewise, a selection of other packages is marked with a 'front-end'
tag.

This tag is then used to break our long package lists in the
documentation into math, front-end, and other packages, for better
navigability:

https://deploy-preview-37315--
sagemath.netlify.app/html/en/reference/spkg/

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URL: #37315
Reported by: Matthias Köppe
Reviewer(s):

Author: Release Manager