`hitTolerance` support

[aocneanu]

Description

This MR adds support for hitTolerance:

Hit-detection tolerance. Pixels inside the radius around the given position will be checked for features. (from ol docs)

Motivation and Context

It's a useful feature when interacting with multiple layers/geometries.

How Has This Been Tested?

Was not tested.

Screenshots (if appropriate):

Types of Changes

• [ ] Bug fix (non-breaking change that fixes an issue)
• [x] New feature (non-breaking change that adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly. -> I would but I'm not sure how to