Add support for substrate following uos

[amaury1093]

• Add support for substrate. QrSigner now support 2 networks: ethereumLegacy and substrate
• removed package-lock, used yarn. i ran npm install and got a bunch of access denied stuff, so switched to yarn asap. Maciej tell me if you prefer to stick to package-lock.

@maciejhirsz If I have your green light, I'll start updating docs

Note: to run the example, I did:

yarn build && cp ./dist/* ./example/node_modules/@parity/qr-signer/dist
cd example
yarn start

TODO:

• update docs rendered README

[amaury1093]

What should we do in case the user inputs a wrong network/payload combo? Right now I'm just showing this ugly div, and also added an onError prop

[maciejhirsz]

I think that's reasonable, the burden of correctness is on the API consumer (!== end user) in this case.

[Tbaut]

Thank you so much for this PR :)
Actually we switched Parity Signer back to yarn so I'm personnaly totally fine for yarn

[jacogr]

I see this in the spec as well, but really dunno how it is relevant. So, I scan the account, the dapp that has that address couldn't care less if it is ed25519/sr25519 or something else. The signer knows and manages the keys.

So basically, the dapp will only send the data through, the mobile signer can sign it with whichever crypto it has created the account with, the dapp really should not need to know or specify crypto.