Ship v4.1.0 (twbs#26218)

* update docs path from docs/4.0/ to docs/4.1/

* bump version to 4.1.0

* Update redirects to work for 4.1 docs move

* Update docs version switcher to include latest and link to 4.0 docs

* re-run dist

* Update package-lock.json

* Update docs-navbar.html

Remove -Pre from Nuget install info since we're stable now /cc @super…

…gibbs

Update version to 4.0.0-beta.3

typo

bump to beta

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prep release

Regenerate Customizer JavaScript

[ci skip]