Anchor point component and jump menu feature on Hero

[AccessPaul]

• Introduces an 'Anchor point' component which can be placed between other paragraphs to create places to scroll or jump users to.
• Adds a small amount of JavaScript to the paragraph edit form so that the use can see what the #hash will be so they can construct external URLs.
• Adds a checkbox to the Hero component to toggle the display of a jump menu on the page. The jump menu aggregates all Anchor points on the page and displays they as a menu, just below the hero. The jump menu is styled to be sticky when the user scrolls down the page.
• Adds JavaScript which creates a smooth scrolling affect when the user clicks a jump menu item.
• Adds JavaScript which marks the relevant jump menu link when the anchor point is scrolled in to view. This link remains active until the next anchor point is reached.

Desktop initial state:

Having scrolled down, menu is sticky and item is visually active:

Mobile initial state - jump menu is horizontally scrollable:

Mobile scrolled state:

Jump menu option on Hero paragraph:

Anchor point paragraph - the URL hash indicator updates as the user types the anchor point label:

[iamsophiesk]

This is such a cool feature. Looking forward to going through the code at some point this week :D