feat: add BULL by Bull Bitcoin

[ethicnology]

Adds BULL as a mobile wallet to the Wallets section.

Supported by Bull Bitcoin

[crwatkins]

Thanks for your submission! Please review guidelines for adding a wallet. In particular please refer to the length of the description, guidelines for trademark capitalization, and the specifications for submitted icons and screenshots.

Have you carefully reviewed the list of requirements and believe that the wallet meets all of those requirements?

[crwatkins]

@ethicnology The bitcoin.org build server was down when you pushed your commits. It's back working now. If you would push a new commit, it will perform some basic testing and schema checking on your submission. Thanks.

[ethicnology]

@crwatkins I've updated the images using magick convert and optipng.
The ratio 250x350 for the mobile screenshot doesn't look good

[crwatkins]

You may have noticed that the CI has failed on your submission due to a missing privacy field. Could you look into that and correct it to proceed? The wallet files here are fairly arcane, so if you need any help on the syntax or the field definitions, please ask here.

[ethicnology]

@crwatkins thanks for your support, CI is good now