Log Message:
unicode-emoji: update to 12.0.

Upstream announcement:
 https://unicode.org/emoji/charts-12.0/emoji-released.html

 Emoji Recently Added, v12.0

 The following emoji characters and sequences have been added to
 this version of Unicode Emoji. Platforms are included where
 images have been made available (however, the images may be
 development versions). The skin-tone variants are not shown,
 but are listed in the counts at the end.

 The characters were based on proposals received by the Unicode
 Consortium, reviewed by the Unicode Emoji Subcommittee, and
 selected on the basis of the Emoji Selection Factors in
 Submitting Emoji Proposals. That page also describes the
 Process and Timeline for proposals.