Unifiy titleFontSize

[DavidLibeau]

Some charts have titleFontSize with a default value set to '1rem' and others set to '0.95rem'.
For consistency, I think that all charts should have the same default value.

[jwilber]

It's set as follows on charts:

style('font-size', (this.titleFontSize === undefined) ?
        `${Math.min(40, Math.min(this.width, this.height) / 5)}px` :
        this.titleFontSize)

Not sure where you're getting the 1rem from?