Parity Signer QR support

[jacogr]

• Groundwork for Add Parity Signer compatibility #355
• Replaces old work from QR display and reading (Parity signer compat) #564 (based on next, way too outdated to attempt a merge - manual merge/rework here instead)

Next steps: Actually making in work in accounts and the signer. When that is done and confirmed working, the ui-qr package should be moved to the ui repo (Just kept here for now while things may still change)

[amaury1093]

i wasn't aware that UOS integration was done already. One comment about Uintarray -> string conversoin

[amaury1093]

There might be bugs with this. if each byte is <128, then it's okay, because the utf-8 encoding will also be one byte. If not, then not sure.

Created this yesterday: kazuhikoarase/qrcode-generator#73

[jacogr]

Yes, I'm very, very worried about that. The TextDecoder/Encoder polyfills (as supplied to RN) is actually the right way, it just uses fromCharCode - so will bring that in here, we don't have an export for it in util.

https://github.com/polkadot-js/common/blob/master/packages/util/src/string/toU8a.ts#L7

[amaury1093]

I think this would work. qrcode-generator is using .charCodeAt to do string->Uint8Array conversion, and we're using .fromCharCode to do Uint8Array->string. They are both inverse functions from each other on 0-255

redundant work to do, but it works.

[polkadot-js-bot]

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