Introduce trusted section wallet discovery

[mjuchli-da]

Add a wallets.json list to carry all trusted wallets, identified by

• provider name
• extension id
• download url
• dapp url
• logo
• (or similar)

Document it so that wallet providers understand that they can open PR's to get listed.
Once listed, we will list the wallet in the picker. If the wallet is a browser extension and is not installed, we link to the download url (e.g. chrome store).