Add stackblitz

[dbanksdesign]

Description of changes

• Add's an open in stackblitz button for applicable examples. Because we use named exports it is a bit more difficult to do.I wanted to open this up so people could give feedback before I add change a bunch of docs files.
• Some minor layout optimization for example code blocks

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Description of how you validated changes

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Checklist

• [ ] PR description included
• [ ] yarn test passes
• [ ] Tests are updated
• [ ] No side effects or sideEffects field updated
• [ ] Relevant documentation is changed or added (and PR referenced)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

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Latest commit: 0eeb2562585fadd078dc99662c3a08b3229cfd8e

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[jacoblogan]

Updated this draft PR to bring it up to date with main, but this feature is currently blocked on resolving some performance issues we are seeing with running amplify apps in stackblitz