SIP-20: WebSockets rewrite (#176)

* wip: SIP-20 rewrite

* Expand SIP

* Apply requested changes

* Update SIPS/sip-20.md

Co-authored-by: Frederik Bolding <frederik.bolding@gmail.com>

* update error handling sentence

* avoid repetition of `This SIP proposes....`

* address requested changes

* update data object

* correct naming

* remove event properties description

* Update SIPS/sip-20.md

Co-authored-by: Frederik Bolding <frederik.bolding@gmail.com>

* Update SIPS/sip-20.md

Co-authored-by: Frederik Bolding <frederik.bolding@gmail.com>

* use `url` instead of `origin`

* add `wasClean` to close event

* Update SIPS/sip-20.md

Co-authored-by: Daniel Rocha <68558152+danroc@users.noreply.github.com>

* Remove error event

* Update wording around open connections

* Apply suggestions from code review

Co-authored-by: Maarten Zuidhoorn <maarten@zuidhoorn.com>

* Update sip-20.md

* Update SIPS/sip-20.md

* Update SIPS/sip-20.md

Co-authored-by: Maarten Zuidhoorn <maarten@zuidhoorn.com>

* Update sip-20.md

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Co-authored-by: Guillaume Roux <hello@guillaumerx.fr>
Co-authored-by: Guillaume Roux <guillaumeroux123@gmail.com>
Co-authored-by: Daniel Rocha <68558152+danroc@users.noreply.github.com>
Co-authored-by: Maarten Zuidhoorn <maarten@zuidhoorn.com>

Author: 4 people