Docs: strip trailing slashes

[archiewood]

Description

• Ahrefs flags this as an issue, as we have links both with or without trailing slashes. This creates duplicate pages that are indexed i.e.
  • docs.evidence.dev/components/bar-chart
  • docs.evidence.dev/components/bar-chart/
• These pages then split the traffic from search engines, diluting them
• This PR consistently applies no trailing slashes, ie docs.evidence.dev/components/bar-chart
• A product side feature to fix this would be to explicitly add canonical urls to all pages

Checklist

• For UI or styling changes, I have added a screenshot or gif showing before & after
• I have added a changeset
• I have added to the docs where applicable
• I have added to the VS Code extension where applicable