Integrate simple asset trade / swap within Krievo/Virto

[monsieurbulb]

Add a simple asset conversion feature to Krievo/Virto app focused on primary assets launching / growing from the krievo ecosystem of collectives and allowing incoming liquidity from kusama and polkadot.

• KSM
• KAB
• DOT
• dUSD

Enable trading of pledged NFTs at some point see #60

[olanod]

The virto.app should/will expose a simple asset swapping functionality in the user account page. We would initially use AssetHub but can consider adding our own asset conversion instance in the future.