Allow plot_heatmap to take boolean arguments

[ulupo]

Reference issues/PRs Follows observations made in #442.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Description A simple multiplication by 1 is used to automatically cast data to a numeric dtype. In this way, boolean arrays are allowed in plot_heatmap.

Checklist

• [x] I have read the guidelines for contributing.
• [x] My code follows the code style of this project. I used flake8 to check my Python changes.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed. I used pytest to check this on Python tests.

[ulupo]

@gtauzin attracting your attention to this as it will be relevant to #442 if merged.