* Bump version to v4.6.1

* Dist

Closes #34146 

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Not sure what happened but indeed, [our current `$secondary` is not what's shown in docs](https://github.com/twbs/bootstrap/blob/c2f949c1fdad09e30793b533e5502808c5e2d423/scss/_variables.scss#L68).

* Bump version to v4.6.0.

* Dist

* Revert colors.yml accidental changes

* Bring colors data files up to par with the vars

This commit includes all the needed workarounds and most changes from the main branch for everything to work, like:

* removing empty lines in raw HTML that break output
* read .browserslistrc, CSS variables from disk instead of duplicating it
* using Hugo mounts
* using Hugo for the docs CSS/JS
* move ToC Sass code to a separate file while adapting it for Hugo

Thus, this patch makes our npm scripts faster since lint runs on one step and there's no separate docs assets processing.