Highlight words to avoid

https://www.pivotaltracker.com/story/show/67482848

As a content designer,
I want to know if I have used a word from the [GOV.UK "Words to avoid" list](https://www.gov.uk/design-principles/style-guide#writing-plain-english),
so I can check if my use of it is appropriate, and avoid making a style guide error.

Edit:

We have re-organised content in the "Formatting help" sidebar tab, which is now called "Help".