add beacon to find out whether localStorage and sessionStorage work on page loads

we want to know so we can tell if it's worth to add personalisation settings into there

we are going to add a test for indexedDB as well in another PR
the linked document http://javascript.crockford.com/code.html .. is really weird - suddenly he just says "Avoid conventions that demonstrate a lack of competence." without explaining what he means!  Also he advocates declaring variables in alphabetical order which is really strange!  If you have enough to cause that problem, alphabetical order surely won't help?