steem:// is not a whitelisted scheme, use web+steem://

[pauliusuza]

According to WHATWG standard, steem:// cannot be used as a uri scheme because it's not whitelisted, and this specification should be using web+steem:// instead.

https://html.spec.whatwg.org/multipage/system-state.html#custom-handlers

I can confirm that steem:// does not work as a protocol handler from within web extensions on Firefox and Chrome, but web+steem:// works just fine.

[pauliusuza]

steemuri.decode() fails if incorrect protocol is detected:
Error: Invalid protocol, expected 'steem:' got 'web+st'

It should support all three possible formats:

• steem://
• web+steem://
• ext+steem://