Repaint Fixes When Scrolling

set not-allowed cursor on disabled radio+checkbox labels

replace SemVer summary with a link to its website

Closes #13702 by merging a rebased version of it.

Proposed fix for #13268

Improve JS style

Good catch @juthilo
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Hopefully fixes trigger focus restoration on modal close

`slideIndex` is assigned to the same value a few lines above.

Be more consistent across the whole codebase.

Also, make use of JSHint's 2.5.1 `extends` and `qunit` options. This way we set our basis options in js/.jshintrc and override the rest.

Customizer: Alert on successful save to Gist

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Added rename directive for composer

Bump grunt-saucelabs to ~8.0.2

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Bump dependency versions

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Changed broken #authors anchor to #creators

add missing role="menu" attrs to .dropdown-menu elements in docs+examples

Docs audit prompted by #13697.
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