MDL-58040 blocks: add upgrade.txt note
A major upgrade from 14.10.0 to the 15.0.0 version will be performed on Friday, May 27 starting at 8 pm UTC up to 8.20 pm UTC. A short 20 min downtime is expected.
|This files describes API changes in /blocks/* - activity modules,|
|information provided here is intended especially for developers.|
|=== 3.3 ===|
|* block_manager::get_required_by_theme_block_types() is no longer static.|
|=== 3.1 ===|
|* The collapsed class was removed from the navigation block to make it compatible with aria.|