calendar-row: Add a popover to explain about read-only calendars
When a calendar is read-only, a lock icon appears and the tooltip of this icon shows the "Read-Only Calendar" text. However:
- Tooltips won't work in a touch device
- Orca doesn't read this text
To fix this, use a button with a popover, which contains a text explaining that the calendar is read-only.
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Edited by Automeris naranja