feat/playground-second-iteration

This contains fixes and improvements to the new playground feature:

The playground will now search for feature toggles automatically if the URL contains a valid query
The playground defaults to the first available valid environment
Moved context form above the JSON field
Fixed a bug where placeholder would display in search
Changed the layout to keep the results on the side
Added date input for currentTime and legal values dropdown
Added sticky form
Added variant popover information
Added ability to search for isEnabled result
Added CodeMirror JSON editor

Unleash / unleash-frontend