Extensions (#737)

- add the current document title in the toolbar
- allow user extensions to define optional parameters
- more events for renamedElement, beforeClear, afterClear, sourceChanged
- remove "message" event used for iframe integration not used anymore. can be readded through a new extension if necessary
- default precision down to 2 digits (and applied in rotation)

cypress/support/ui-test-helper.js

@@ -3,6 +3,7 @@ export const approveStorage = () => {
 }
 
 export const visitAndApproveStorage = () => {
+  cy.viewport(512, 512)
   cy.visit('/instrumented/editor/index.html')
   approveStorage()
 }