Boltcard/LNURLw support #331
Description
Support for withdrawing from Boltcards would be awesome, and basic LNURLw support gets us 80% there.
If we register the lnurlw:// schema as belonging to our app any scans of NFC tags with such an URL will be forwarded to the app. It's important to support LUD-17 LNURLw for Boiltcards, since they dynamically generate the URL and can't wrap it in bech32.
More details here: https://github.com/boltcard/boltcard/blob/main/docs/SPEC.md
As a stretch goal we could intercept all NFC scans while the app is open to avoid the OS showing the user a choice between different apps supporting LNURLw when they scan a NFC tag while the app is open.