[Feature Request] Emoji selection when typing : (colon) symbol in the chat box

### Description of the issue
I would like to request a feature for selecting emoji when typing colon in the chat box, for example typing :joy will show a selection of emoji to choose.

### Your environment
* Version of huly: [huly.app](huly.app)
* Browser (and version): Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15
* Your operating system (and version): macOS Sequoia 15.0

### Steps to reproduce
Type something like :joy in the text input in chat.

### Expected behaviour
A selection of emojis would show up. (screenshot from Slack)

### Actual behaviour
Nothing happens on Huly.

### Possible solutions
Since we already have user selection when typing with @ (at) symbol, I think a similar solution can be implemented when typing the : (colon) symbol, but for searching emojis instead.

Start at the chat box text input and trace the existing user-selection flow triggered by @, which the issue identifies as a similar entry point. Implement the corresponding emoji-selection behavior for colon searches such as :joy, then verify that matching emoji choices appear while typing and can be selected.

Written by the indexing model from the issue text.