fix(ui): fix iframe height styles

[jrson83]

• add scrollbar example to docs & react
• fix component bottom getting trimmed
• fix app height getting trimmed when viewing story in new tab
• remove 100vh beeing applied to iframe, fixes app viewport much too large on mobile devices

closes #54

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (8e4e278) 2.80% compared to head (b703bb8) 2.80%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #56 +/- ## ===================================== Coverage 2.80% 2.80% ===================================== Files 44 44 Lines 2746 2746 Branches 57 57 ===================================== Hits 77 77 Misses 2626 2626 Partials 43 43 ```

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