Docs: Changes corresponding to docs design updates

[kylegach]

What I did

See also: storybookjs/frontpage#626

• Remove emoji from and simplify top-level titles
• Remove concept of bullet-link
• Remove /<renderer> from URLs in the CLI templates
• Remove /<renderer> from URLs in the docs
• Update TOC to use heading type
  • Rename introduction.md, overview.md, how-to-contribute.md pages -> index.md pages
  • Add all-new index.md pages for Sharing and API
  • Add redirectPath to get-started TOC item
    • Temporary workaround until we build a proper docs homepage
  • Find/replace introduction.md/overview.md -> index.md
  • Find/replace /introduction//overview -> /
  • Add hideRendererSelector: true to frontmatter of (some) pages that aren't conditional on renderer

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli/src/sandbox-templates.ts

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>

[jonniebigodes]

@kylegach, one small item here. I suggest removing the framework in the links for our addons and providing with the installation process. Reasoning here: if the reader checks this but is working with Vue or has checked our Vue docs, they should not see a framework that's not his own. This leads him to have to go up the page and select another renderer just to see what wants to read about, otherwise it should automatically default to React.
Just trying to keep it consistent, and I'll leave it to you to proceed.

[kylegach]

This PR corresponds with one in frontpage that completely removes the renderer from the URL. URLs containing a renderer will redirect to the the correct renderer-less URL with zero affect on whatever renderer is in their localStorage and used for the site.

[kylegach]

Additionally, I opted to not remove the renderer from the various URLs in READMEs in this PR. While most renderers only have a few results, react has 150+ and I didn't want to make this one any bigger than it needed to be.

[jonniebigodes]

Thanks, @kylegach, for putting this pull request together and significantly improving the documentation. I've checked a few small items for you to consider when you have a moment. To unblock you, I'm approving the pull request.