Pervent overlapping external labels in pie chart

[xychang]

Description

Currently when there are multiple small categories in pie chart, the external label would overlap with each other.

This change will prevent it from happening but moving down the label up on detecting overlap.

Type of change

Please delete options that are not relevant.

• 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 not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• If this is a bug fix, did you add or update a test file to the examples directory that verifies the bug is fixed?
• If this is a new feature, did you add files to the examples directory to demonstrate the feature?
• If this is a new feature, did you add documentation to the docs directory for the feature?

[lazyguru]

Thanks for your contribution