how_to_add _a_wallet.md

what to do when adding a new wallet:

• add wallet symbol name in Wallet.Names exported string array

• add wallet string name in Wallet.stringNames exported string array

• implement Wallet.enable

• implement Wallet.isEnabled

• implement Wallet.has

• implement Wallet.isAviable

• implement Wallet.get

• implement Wallet.getInterface

• implement private_makeWalletInterface function

• implement Error

• add Error export