Spotlight - Prediction Market - Prediction Market creation form - filter out known assets

**Is your feature request related to a problem? Please describe.**
Disable or filter out known assets from being input into the symbol creation field

**Describe the solution you'd like**
Prevent the user from creating a symbol already in use on the DEX

**Describe alternatives you've considered**

- An alert/pop up if a known symbol already in use is entered into the symbol field.

- Red colored lettering for known or in use symbols; Green colored lettering for unknown or not in
use symbols

The issue does not name files, tests, or an entry point. Start by locating the prediction market creation form and how it checks symbols against assets already in use on the DEX. Done means a known symbol cannot be created and the chosen alert or color feedback is visible to the user.

Written by the indexing model from the issue text.