api_docs: Add "EmojiCode" common component.
api_docs: Add "EmojiCode" common component.

To facilitate re-use of the same parameters in other paths, this commit
store the content of the parameter "emoji_code" in components.

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