DEMO: uses `height`, DOCS: uses `thickness`

[Johnsoct]

Desc

In the demo, your options use height for the height option, but in the documentation, it uses thickness, which is the correct property to affect the height of the progress bar.

Dev options

Choose thickness as the property name and make the change on the documentation instead of breaking tons of applications.

Notes

Related to #67

[Tardigrada777]

I noticed it too!