`ChakraUIRenderer()` accepts `theme.heading` but never uses it

[reminjp]

Since the ChakraUIRenderer's first arg is typed as theme?: Defaults, it accepts heading. However heading is never used.

I think there are two ways to fix it:

• Change the type of theme from Defaults to Components.
• Assign theme.heading to theme.h1, ..., theme.h6 before deepmerge(elements, theme).