Adjust typography on the example page

[przemyslawzalewski]

The following typographic issues were fixed/adjusted:

• The footer text is now always centered
• Line heights were increased to 170% of the font size
• Horizontal margins for text copy was introduced to never make it stick to the phone chrome or screen borders
• Fallback text for action trigger status is now displayed to prevent empty space being shown until the user triggers some action
• A more semantic h1 tag replaced the h3 tag of the page title but still uses the same styling.

[marekrozmus]

@all-contributors please add @przemyslawzalewski for code, ideas

[allcontributors]

@marekrozmus

I've put up a pull request to add @przemyslawzalewski! 🎉