PLANET-5227 Counter Block Accessibility

[comzeradd]

Brief summary of task:

Improve a11y status of the Counter block markup

Objectives of task:

The counter block looks pretty good, VoiceOver reads the text separately if it has placeholder, for example:

700
signatures of
1000
completed
300
remaining

To avoid this, add a "role=text" attribute to the "counter-text" div.

[comzeradd]

Fixed at greenpeace/planet4-plugin-gutenberg-blocks#366