Contain:strict breaks css counters

[5e-Cleric]

The Contain property was set to size previous to this version, but it was set to strict in #3965 . This property is isolating pages, which in time makes CSS counters impossible to use, as per the documentation:

• style
  This value turns on style containment for the element. This ensures that, for properties which can have effects on more than just an element and its descendants, those effects don’t escape the element.

• strict
  This value computes to size layout paint style, and thus turns on all forms of containment for the element.

We may look for lighter forms of performance optimization, as not to break existing features. This property should be removed whenever possible, and perhaps set as an extra setting that must be turned on by the end user with acknowledgement of the consequences.