ui: eth/token wallet setup hints

[norwnd]

Embed the link to wiki page from #2233 somewhere in UI (somewhere visible, like on create and reconfigure ETH/Token wallet forms highlighted with red) so that user is prompted to read Ethereum tutorial.

Expecting users to find it on their own is probably a set up for countless help-requests in decred support channels.

I think overall approach of hint-on-need-to-basis is more practical than having a separate wiki and expecting users to read it before using DEX.

[buck54321]

Can add a field for a link to the WalletDefinition and display the link on the create/reconfig form (or hide link element if field is empty). Can I assign you, @norwnd?

[norwnd]

Yep!