️🛠 - Add network initials to Network Cards in case there is no avatar

[Tuditi]

Task description

When a custom network doesn't have an icon, we should show it's initials.

https://github.com/bloomwalletio/bloom/blob/dbe5669e8c56d584dc224b770e1f6d30813d1b53/packages/shared/src/components/avatars/NetworkAvatar.svelte#L37

Requirements

TBD

[Tuditi]

Addressed in https://github.com/bloomwalletio/bloom-private/pull/17