Check/improve screen reader accessibility

[karllhughes]

I've done some basic checks on this, but would love help with more in-depth coverage making sure this app works well for users with accessibility issues.

[karllhughes]

There are two major issues spotted by @hollielu:

• When you navigate to each page the title is read first and then the focus does not move logically from the top of the page down, it starts on a random element.
• On the Create Rubric page when you create a new component the focus should automatically move to that new component. Currently you have to tab up 37 times to get to it.