Use `emoji.json` to create a emoji catalog and add it to
`emoji_code.js` file. This catalog contains the unicode
codepoints of all the emojis grouped according to their
category. Emojis are sorted according to the `sort_order`
defined in the iamcal's dataset.
Previously, if you searched for ':offi..' you would see both 🏢 and
:office_building: as possible completions, both of which are shortcodes for
the same unicode codepoint (and hence which have the same image). Also, we
sort the emoji in our emoji pickers alphabetically by shortcode, and so the
images for 🏢 and :office_building: show up next to each other, which
looks like a bug. This removes :office_building: as a shortcode, along with
several hundred other duplicates. It leaves some duplicates in that won't
give autocomplete or alphabetical ordering a problem, like (🚗,
:automobile:).
