React to theme changes in widget mode

[robintown]

Part of the fix for element-hq/element-web#27671
Depends on:

• Expand support for MSC2873 (changing theme/language) matrix-org/matrix-widget-api#117

• Export theme and language action types matrix-org/matrix-widget-api#119

• created issue for the rust-sdk widget driver

[hughns]

Need to fix the lint errors, which I think will then show the typings errors due to dependency on the unmerged PR in matrix-widget-api.

Please can you add the necessary version bump to package.json and yarn.lock?

Some comments inline.

[robintown]

Lints fixed, I plan to bump the matrix-widget-api version once the linked PR is reviewed and released. (That's what I should've used the 'blocked' label for)

[toger5]

The rust widget driver does not send the theme change action iirc.
I will check if it at least the url property is set by the rust sdk. (edit: url properties are supported by the rust sdk)
Can we create issues for the rust-sdk repo to add those features as port of this pr?

[hughns]

I've merged matrix-org/matrix-widget-api#119 so I think this PR is now unblocked.

[hughns]

Marking as draft until updated with the upstream dep to fix the typechecking.

[hughns]

Looks good 👍