Prepare WordPress core to MediaElement to 3.x

[isantolin]

Hi to all:
MediaElement is nearly close to release 3.0.

​https://github.com/johndyer/mediaelement/tree/3.x-dev/

Anyone can try to replace Mediaelement 2.x with 3.x?

[isantolin]

Now, version 3.0 is out

[ocean90]

Hello @isantolin, welcome to Trac!

Thanks for your request. The current maintainer has opened a new ticket for this with more details so I'm closing yours as a duplicate of #39686.