ARIA - add aria-label on topic input and post textarea (PR #10057)

Add reply form role with label as create/reply, and aria-labels on text inputs

Regarding d-textarea - Is this the only/best way to add html attributes to predefined components, until Ember Octane and Glimmer components are more widely used?

GitHub

This pull request has been mentioned on Discourse Meta. There might be relevant details there:

https://meta.discourse.org/t/aria-composer-window-elements-are-not-being-read/154600/2

Regarding d-textarea

Seems good to me!