emoji_codes: Replace JS module with JSON module.

webpack optimizes JSON modules using JSON.parse("{…}"), which is
faster than the normal JavaScript parser.

Update the backend to use emoji_codes.json too instead of the three
separate JSON files.

Signed-off-by: Anders Kaseorg <anders@zulipchat.com>

static/js/markdown.js

@@ -6,6 +6,8 @@
 
 // Docs: https://zulip.readthedocs.io/en/latest/subsystems/markdown.html
 
+const emoji_codes = require("../generated/emoji/emoji_codes.json");
+
 let realm_filter_map = {};
 let realm_filter_list = [];