feat: add megalith LSP

[rolznz]

LSPS1 LSP for incoming liquidity with 0-conf and minimum size of 20,000 sats.

https://docs.megalithic.me/

[MegalithicBTC]

Just adding a direct link to the relevant docs, instead of the main docs page: https://docs.megalithic.me/lightning-services/lsp1-get-inbound-liquidity-for-mobile-clients