emoji_picker: Add test that all emoji are in categories.
emoji_picker: Add test that all emoji are in categories.

This should prevent the category of bug seen in the last commit.

kou/zulip,showell/zulip,kou/zulip,hackerkid/zulip,punchagan/zulip,kou/zulip,zulip/zulip,timabbott/zulip,andersk/zulip,showell/zulip,showell/zulip,shubhamdhama/zulip,synicalsyntax/zulip,hackerkid/zulip,timabbott/zulip,synicalsyntax/zulip,timabbott/zulip,showell/zulip,eeshangarg/zulip,eeshangarg/zulip,timabbott/zulip,rht/zulip,brainwane/zulip,zulip/zulip,synicalsyntax/zulip,shubhamdhama/zulip,rht/zulip,zulip/zulip,eeshangarg/zulip,kou/zulip,showell/zulip,andersk/zulip,kou/zulip,eeshangarg/zulip,zulip/zulip,brainwane/zulip,hackerkid/zulip,kou/zulip,brainwane/zulip,andersk/zulip,brainwane/zulip,eeshangarg/zulip,hackerkid/zulip,shubhamdhama/zulip,rht/zulip,eeshangarg/zulip,shubhamdhama/zulip,brainwane/zulip,synicalsyntax/zulip,synicalsyntax/zulip,punchagan/zulip,shubhamdhama/zulip,rht/zulip,punchagan/zulip,andersk/zulip,andersk/zulip,showell/zulip,punchagan/zulip,showell/zulip,hackerkid/zulip,rht/zulip,hackerkid/zulip,synicalsyntax/zulip,timabbott/zulip,brainwane/zulip,shubhamdhama/zulip,punchagan/zulip,timabbott/zulip,synicalsyntax/zulip,brainwane/zulip,timabbott/zulip,kou/zulip,eeshangarg/zulip,rht/zulip,punchagan/zulip,rht/zulip,zulip/zulip,zulip/zulip,shubhamdhama/zulip,punchagan/zulip,zulip/zulip,andersk/zulip,hackerkid/zulip,andersk/zulip