Is your feature request related to a problem? Please describe.
We are hardcoding some font configurations like the fontVariant and the fontWeight when rendering the axis title.

Describe the solution you'd like
We should expose those into the Theme making them configurable directly.

Describe alternatives you've considered
n/a

Additional context
We are hardcoding those values both on the cartesian charts and on the heatmap chart. We should align those and use the theme object across charts