Bk/improve overlay documentation

[bryankeller]

Details

This fixes an issue that caused the tooltip view in the example project to capture touches, preventing other days from being selected.

Related Issue

#263

Motivation and Context

Clarify documentation about tooltips so people are less likely to get stuck on this odd behavior.

How Has This Been Tested

Example app

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.