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wait 25ms to determine if an element is really visible in the viewport

This is not an issue since we also use the offset parameter
simple refactor around viewport compute

viewport is always at least the offset, we then add it the real viewport
lower the scroller timeout for tests

scroll should be faster than the debounced functions of inviewport
scroll check.

To be able to simulate FAST scrolls

Also make playground at top and the smallest possible
v0.2.1