Add skip link to stats and analytics pages

[aitchiss]

What type of PR is this? (check all applicable)

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update

Description

This PR adds the skip link functionality to the analytics dashboard and the article stats pages, along with a 'main' landmark. Due to the way we transition between pages at the moment, the skip link is currently only the first focusable element on a fresh page load.

As part of #1153 we will want to change that, but it can be done as a final step once the functionality is ready on all of our pages.

Related Tickets & Documents

#1153

QA Instructions, Screenshots, Recordings

• Go to /dashboard/analytics
• If you navigated there by a link click, refresh the page (as per above note on fresh page loads)
• Press the Tab key and check the skip link appears
• Click the skip link with either the Enter key or the mouse
• Press Tab again and check the next focused element is the Week/Month/Infinity links
• Go to one of your user's published articles and click the 'Stats' button
• Refresh the page as per above note
• Tab and check the skip link again, same as above

CleanShot.2021-04-23.at.15.33.37.mp4

UI accessibility concerns?

This adds an essential accessibility feature for keyboard users, as well as the required main landmark.

Added tests?

• Yes
• No, and this is why: Cypress can't yet test the Tab event properly, so for now this has to be a manual check
• I need help with writing tests

[Forem core team only] How will this change be communicated?

Will this PR introduce a change that impacts Forem members or creators, the
development process, or any of our internal teams? If so, please note how you
will share this change with the people who need to know about it.

• I've updated the Developer Docs and/or
  Admin Guide, or
  Storybook (for Crayons components)
• I've updated the README or added inline documentation
• I will share this change in a Changelog
  or in a forem.dev post
• I will share this change internally with the appropriate teams
• I'm not sure how best to communicate this change and need help
• This change does not need to be communicated, and this is why not: this is part of the wider A11y: provide content skip links for keyboard/screen reader users #1153 issue and we can communicate the changes as a whole once complete

[optional] Are there any post deployment tasks we need to perform?

[optional] What gif best describes this PR or how it makes you feel?