* use descriptive docs btn naming
* rename `btn-bd-yellow` to `btn-bd-download`
* sort state vars
* sort state vars
* info, warning, danger
* rename btn-bd-purple
* rename `.btn-bd-purple` to `.btn-bd-primary`
* align docs color variables
* generate $bd-purple-light color
* with http://razorltd.github.io/sasscolourfunctioncalculator/
* allow overide of docs variables
* use a trailing slash when possible
* use https when possible
* remove a few redirected links
* consistently use `https://popper.js.org/`
* fix `iconUrl` in nuget files
* change Jekyll Windows guide to the official one
* Add explicit aria-label attributes to <svg> based links
As some browser/AT combinations don't seem to fully support grabbing the
`<title>` from inside the `<svg>` as the link text/name to announce
(e.g. Firefox+NVDA)
* Add <title> to Bootstrap logo <svg>
* Add <title> to menu <svg>
* Add explicit focusable="false" to <svg> icons
Due to a bug/"feature" in IE, `<svg>` elements are usually separately
focusable, which then results in links with `<svg>` icons being
essentially focused twice (once for the link, and once for the `<svg>`
inside, which is then also non-interactive)
