Solution mentioned by Chris Baswell at https://stackoverflow.com/a/45969088

Since flex-order was renamed to just order, change the subtitle.

I feel like `auto` is missing from the values here and that it should be there. Although it is mentioned below, only a single use case, whereas in other sections it appears with the option to set the left margin of an element to auto, for example.

Remove accidental `alt` addition from Bootstrap stack image.

Check `form-control-focus` mixin, variable name is `$input-focus-border-color`

We can check for browser compatibility on lint time now.

This is so other plugins can use it too.

* 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

`abs()` gets the absolute value of `$level`.
That way, `if/else` statement can be completely eliminated.

Add .txt and remove the non-existent .py files.

This way, it's run for us automatically after `docs-compile`.

Switch all instances to `sh` but keep `bash` so that things won't break either way.

* ignore `twbsconfig.yml`
* add a trailing slash for folders

Before: 312 KB (320.250 bytes)
After:  253 KB (259.961 bytes)

* Use `aria-selected` instead of `aria-expanded`
* Change tab.js to use `aria-selected` rather than `aria-expanded`
* Add `aria-orientation=vertical` to vertical tab list
* Remove dynamic tabs with dropdowns
* Fix non-interactive code examples
* Only set `aria-selected` on the `role="tab"` trigger - this stops `aria-selected` being incorrectly added to the `role="tabpanel"` itself (probably harmless, but nonetheless incorrect)

* fix(scrollspy): Handle nested navs when nav-link inside nav-item

* [scrolspy] Find only child .nav-link's inside .nav-item

* [scrollspyt] Add tests for nested navs with nav-link inside nav-item

* fix troy-o's in test