Notes on README files update

[migacz1125]

In notes part of description is information to load core, widget, mouse & sortable. In jquery-ui since 1.12 version core.js is deprecated and to be remove in 1.13 version. That will be nice to add some information about this.

[thgreasi]

Thanks for the heads up!

[thgreasi]

Updated README to point to the new dependencies, have an up-to-date custom builder url & contain an updated jsdelivr min dependencies url.
Again, thanks for the heads up.