the problem we fix is that since we add the styles asynchronously, the browsers, esp. Firefox, sometimes apply transitions from the null/default state to the one specified in the injected CSS.
supersedes 72e8213b and 4dbca46b
* in manager use search query like url:https://github.com/openstyles/stylus
* in popup shift-click or right-click on manager button opens it and applies the filter
