heatmap chart update

[apryka]

What does this PR do? How does it affect users?

• css styles updates
• config object updates
• html object or string css selector can be provided

Related tickets?

How should this be tested?

Step through the code line by line. Things to keep in mind as you review:

• Are there any edge cases not covered by this code?
• Does this code follow conventions (naming, formatting, modularization, etc) where applicable?

Fetch the branch and/or deploy to staging to test the following:

• [ ] Does the code compile without warnings (check shell, console)?
• [ ] Do all tests pass?
• [ ] Does the UI, pixel by pixel, look exactly as expected (check various screen sizes, including mobile)?
• [ ] If the feature makes requests from the browser, inspect them in the Web Inspector. Do they look as expected (parameters, headers, etc)?
• [ ] If the feature sends data to Keen, is the data visible in the project if you run an extraction (include link to collection/query)?
• [ ] If the feature saves data to a database, can you confirm the data is indeed created in the database?