MSC4133 - Extended profiles

[Half-Shot]

Disclaimer: This is being worked on with an open source community hat on rather than my Element hat.

For matrix-org/matrix-spec-proposals#4133

While this MSC is in review, I opted to make new methods rather than extend the existing profile methods. I'm open to changing this if that seems more appropriate, but I think it's just as easy to change the methods later once the endpoint stabilizes.

Checklist

• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass.
• [N/A] Sign-off given on the changes (see CONTRIBUTING.md).

[dbkr]

otherwise this looks good I think

[dbkr]

This feels a bit repetitive - maybe a extendedProfilePrefix or something would be useful?

[Half-Shot]

Done.

[dbkr]

Thanks!