* Add dropright (right placement for our dropdown)

* Add dropleft

* moves drop left arrow to the left

We don't support Opera 12, and Firefox's property was the unprefixed one.

Unit test for pull request #24240

Fix for issue #24117

Having it uppercase doesn't offer anything and the lowercase version slightly improves gzip compression.

* Offset option can be function (Popper.js)

* Fix...add function type for offset option

* Remove constants for popper config

* Optimize code. Remove foreach loop.

* Refactoring. Remove getOffset method

We can check for browser compatibility on lint time now.

* 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