Bold font size get's overridden by fontDescriptor

[bensLine]

When using a custom font (e.g. SourceSansPro-Bold.ttf) and configuring it as markdown.bold with custom font size 16 the library returns the font with size 12.

It turned out that font size 16 get's overwridden by the font descriptor in SwiftyMarkdown+iOS.swift:

if globalBold, let boldDescriptor = font.fontDescriptor.withSymbolicTraits(.traitBold) {
     font = UIFont(descriptor: boldDescriptor, size: 0)
}

I'd expect that the library respects the configured font size 16 and does not overwrite it.

Cheers and thanks for the library!