Opt-in donations to Selene devs, Electrum server providers, and/or other (configurable) parties

• Add on some extra outputs for some transactions that includes a small donation to some set of parties
• Make the amounts for each individual party configurable
• Make the interval for each individual party configurable
• Example configuration: Donate 1000 sats every transaction to Selene devs, donate 1000 sats every 10 transactions to Electrum provider, donate 800 sats every 8 transactions to BCH Podcast, donate 546 sats every 6 transactions to BCHN, etc

Alternatively, instead of extra outputs, we could just send a separate transaction. This may be better for privacy (harder to specifically detect selene users via blockchain analysis)