Feature: allow search to take in a RegExp

[sloanlance]

Change emoji.search() to return emoji whose name contains the search string. I can imagine two approaches:

1. Always treat the argument as a substring. E.g., emoji.search('evil') → [{ key: 'see_no_evil', emoji: '🙈' }, { key: 'see_no_evil', emoji: '🙈' }, { key: 'see_no_evil', emoji: '🙈' }]. (Example results not exhaustive.)
   • This is probably easiest and most lightweight to implement, but is not backwards compatible with old code that uses this library.
2. Allow standard regular expressions in the argument. E.g., emoji.search('.*evil') → [{ key: 'see_no_evil', emoji: '🙈' }, { key: 'see_no_evil', emoji: '🙈' }, { key: 'see_no_evil', emoji: '🙈' }]. (Example results not exhaustive.)
   • This may be more complicated, but it will be backwards compatible and it won't return unexpected results.

[Richienb]

Always treat the argument as a substring

I think that is the current behaviour.

Allow standard regular expressions in the argument

We could allow RegExp objects to be passed that are evaluated for each emoji.