Bump Storybook to v6.5.10 and add workaround for heading anchors

[stephiescastle]

Checklist

• Include a description of your pull request and instructions for the reviewer to verify your work.
• Link to the issue if this PR is issue-specific.
• Create/update the corresponding story if this includes a UI component.
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Description

Due to a regression in Storybook, our anchor links in mdx no longer work. This PR updates the Storybook version (for good measure), and also adds manual fixes to the broken anchor links via <span id></span>. This is a known issue and has only been fixed in v7-alpha so far.

Instructions to test

1. npm i
2. npm run storybook
3. test anchor links (usually TOC) at the top of some docs pages

Tested in the following environments/browsers:

Operating System

• macOS
• iOS
• iPadOS
• Windows

Browser

• Chrome
• Firefox ESR
• Firefox
• Safari
• Edge