GetFace returns a font.Face for the given font name.
This supports both TrueType fonts (scaled to the given size and DPI)
and bitmap fonts (which ignore size and DPI).
OpenFont loads a TrueType font by name.
Note: This currently only supports TrueType fonts provided by the gofont packages.
Bitmap fonts like basicfont or inconsolata cannot be returned as *truetype.Font.