Split Unicode emoji into their own script

Split Unicode emoji into their own script

* admin/notes/unicode: Describe how to update emoji for new Unicode release.
* admin/unidata/Makefile.in: Pass emoji-data.txt to
blocks.awk script.
* admin/unidata/README: Add pointer to emoji-data.txt file.
* admin/unidata/blocks.awk: Parse emoji-data.txt, add emoji codepoints
to the 'emoji' script (except for the ASCII ones).
* admin/unidata/emoji-data.txt: New file.
* etc/NEWS: Describe new 'emoji' script.
* etc/TODO: Update item about 'emoji' script.
* lisp/international/fontset.el (script-representative-chars): Add
'emoji' script.
(setup-default-fontset): Add 'emoji' script.  Use "Noto Color Emoji"
as default font for it.