Lets put jquery in the bin

[omidantilong]

Changes:

• Completely removes jquery from the frontend
• Does NOT remove the jquery script tag yet - we should do this separately (it appears to still be used by the mailchimp signup widget)
• All the ui interaction has been rewritten in vanilla js
• Fixes the collapsible menu flicker when navigating between pages in the same section
• Makes the search input more predictable
• Allows closing the menu with a second press of esc, or a single press if the search input does not have focus
• Removes the need to set is-open classes on everything by utilising the cascade
• Uses IntersectionObserver for the back-to-top link rather than binding to the scroll event
• Debounces window resize logic rather than binding to the raw resize event
• Started inline media queries in their parent class where appropriate

This is by no means a total fixup. We should look to move away from gulp (5s compile times 😱 ) and .cjs files, start using prettier (etc) in our local environments, and so on. It would be cool to rebuild this as a next app using the learnings from the workbench project.

But this hopefully puts us in a better place in the meantime.

[matt-tyas]

@omidantilong I missed this. If we can resolve the merge conflict this branch now has I'll take a look and merge it.