Tutorial page improvements

[jcalcaben]

Description

Makes the Tutorial section easier to discover on the front page and add content to the Tutorial overview page.

Related Issue

Closes #1248

Verification Steps

1. Navigate to the pwa-devdocs directory
2. Run the linter: npm run lint src/tutorials/index.md
3. Verify there are no linter issues listed
4. Run the preview server: npm run develop
5. Verify the Tutorial panel is displayed instead of the Tools and Libraries section
6. Click on the Tutorial panel
7. Verify the Tutorial overview page is not bare and contains links to the different tutorials

Checklist:

• I have updated the documentation accordingly, if necessary.
• I have added tests to cover my changes, if necessary.

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