`trigger()` can handle string argument

Original is triggering `affixed` not `affixed.bs.affix`, only `.on('affixed.bs.affix', ...)` also catch `affixed` event.

Closes #13998.

Will hopefully revert this reversion and land a fully-working version of UMD in v3.3.0.

Revert "some changes from #13801 - add strict mode back and =="
This reverts commit 2b302f69.

Revert "Fix regression of #10038 introduced by #13772"
This reverts commit e9d6756a.

Revert "MD/CommonJS/Globals #12909"
This reverts commit 1c6fa901.

Revert "address #13811"
This reverts commit f347d7d9.

Conflicts:
    js/carousel.js
    js/collapse.js
    js/dropdown.js
    js/modal.js
    js/tab.js
    js/tooltip.js

Closes #13782 by merging it.

fixes #13430

fix #13220 Scrollspy generates wrong offsets for a page-- recalculate offsets if `scrollheight` changes

faster and easier to test/develop js functionality not represented in unit tests, and gives us
a playground for interactions, etc.

It also makes it so developing javascript is now decoupled form jekyll, which should make everything
faster and less painful.

This commit also reverts my filter commit https://github.com/twbs/bootstrap/commit/9900771aa7f1b3ddcee49aec84082104776ace70
which broke scrollspy for dropdowns.

Closes #13702 by merging a rebased version of it.