[Enhancement] Option to create a 24-word mnemonic based on two valid 12-word mnemonic

[tadeubas]

Make Krux able to do just like this Double mnemonic generator that creates a 24-word mnemonic where both parts are valid 12-word mnemonics.

The idea is be available at New Mnemonic on the same screen that asks to select 12 words / 24 words, a new item called Double mnemonic. Also on Home > Mnemonic > Words if the 24 words is a double mnemonic, it must show at the bottom the text Double mnemonic