Automate coins fetching from wallet-core

[tw-covain]

In wallet core there is coins list https://github.com/trustwallet/wallet-core/blob/master/registry.json
which is usually used a source for coins.yml.
This is something that can be automated.

Also there should be a possibility to extend the list with some custom coins (that are not in wallet-core). So this should be considered as well.

[optout21]

One concern: handle case when a coin is already supported by wallet-core, but not (yet) bz the iOS/Android app.

Range of data that could be synchronized:

• symbol
• handle (from id)
• name (from name/displayname)
• decimals: 18