|Create a CompatibilityActor.
CompatibilityActor is responsible for providing the compatibility information
for the web page using the data from the Inspector and the `MDNCompatibility`
and conveys them to the compatibility panel in the DevTool Inspector. Currently,
the `CompatibilityActor` only detects compatibility issues in the CSS declarations
but plans are in motion to extend it to evaluate compatibility information for
The design below has the InspectorActor own the CompatibilityActor, but it's
possible we will want to move it into it's own panel in the future.
The InspectorActor that owns this CompatibilityActor.