openapi: Extract Emoji Reaction schema from `Messages`.
openapi: Extract Emoji Reaction schema from `Messages`.

The Emoji Reaction schema is used in multiple place and hence
it is better to have it extracted as another schema in `components`.

punchagan/zulip,hackerkid/zulip,punchagan/zulip,punchagan/zulip,punchagan/zulip,andersk/zulip,eeshangarg/zulip,rht/zulip,hackerkid/zulip,brainwane/zulip,kou/zulip,brainwane/zulip,hackerkid/zulip,kou/zulip,showell/zulip,zulip/zulip,punchagan/zulip,zulip/zulip,brainwane/zulip,brainwane/zulip,rht/zulip,showell/zulip,showell/zulip,showell/zulip,showell/zulip,kou/zulip,andersk/zulip,kou/zulip,eeshangarg/zulip,hackerkid/zulip,punchagan/zulip,rht/zulip,zulip/zulip,andersk/zulip,kou/zulip,kou/zulip,andersk/zulip,rht/zulip,hackerkid/zulip,eeshangarg/zulip,andersk/zulip,brainwane/zulip,rht/zulip,showell/zulip,brainwane/zulip,punchagan/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,rht/zulip,andersk/zulip,andersk/zulip,eeshangarg/zulip,eeshangarg/zulip,eeshangarg/zulip,zulip/zulip,zulip/zulip,brainwane/zulip,zulip/zulip,showell/zulip,kou/zulip,hackerkid/zulip,hackerkid/zulip