accessibility: issue/#2193 General accessibility fixes

[oliverfoster]

#2193

• Centralized breaking behaviour into one place
• Made sure focus behaviour only happens after initial render
• Fixed ios iframe breaking
• Shortened and fixed component description
• Removed role="button"
• Removed a11y_text
• Hidden image in place of label representation
• Used a11y_heading_attrs

List of outstanding PRs: https://github.com/adaptlearning/adapt_framework/issues/2206.

[oliverfoster]

Like that?

[moloko]

Do we need the example JSON and README updating with that _ariaLevel attribute?

We do indeed. And can I just check it's correct that it's defaulted to 0 in properties.schema?

[oliverfoster]

I'd like to put the _ariaLevel bits in the core readme. The are only meant as overrides on the components.

[oliverfoster]

Default 0 is equivalent to "not set" as heading level 0 doesn't exist

[oliverfoster]

@lc-thomasberger could you re +1?