[Feature Request] Support Electrum seedphrase format

[bitcoinprecept]

This topic came up in the seedsigner telegram group. I am not personally familiar with Electrum's seedphrase format, but I understand it is different from BIP-39 and not presently supported by seedsigner. It's potentially worth considering to add support for in the future. Logging this issue to capture the topic for future reference.

[BamaHodl]

I would like this as well. In fact I have implemented it for my own use and it's only a few lines of code to do it in a non-generic way, i.e. it requires storing the status of the seed and using that to change the behavior of seed and tool views.
There may be another way to do this by treating it as another script type, however this has much larger implications for the rest of the code and I wanted to keep my changes as minimal as possible.
I have only implemented the segwit version of electrum seeds. It's a trivial change to add the legacy version if users have legacy seeds they'd like to continue to use.
It should be noted seedsigner doesn't play well with electrum wallet itself currently. However these changes do allow using your electrum seed on the seedsigner and then exporting the xpub to another wallet software with better QR support, e.g. Sparrow.

I will work on adding better QR support to electrum next if I can figure that out.

To view my changes:
dev...BamaHodl:seedsigner:dev

Tested and working for both single and multi-sig wallets using electrum seeds.