docs: update related packages sections

[stdlib-bot]

This PR

• updates the related packages section of READMEs to include links to related packages.

[kgryte]

@Planeshifter For PRs adding new packages, we need to ensure that the related packages section is empty. This is a common occurrence where contributors attempt to manually edit that section, despite the note instructing them not to.

[kgryte]

For now, it is up to reviewers to manually edit that section or leave an instruction for contributors to remove the contents, if they try to include it.

[kgryte]

@Planeshifter This is also an instance where I don't think that the Math label should have been applied. I suggest turning off the auto-labeler entirely.

[Planeshifter]

@kgryte let's first change to only apply Math and BLAS labels if all changed files match the glob pattern. That will prevent labeling in cases like this. I will go further and also disable it for automatic PRs. Will update the config tomorrow.