Add examples that render text with pango

[jackdbd]

Cairo is often used in conjunction with pango to render text.

See:

• https://cairographics.org/FAQ/
• https://wiki.gnome.org/Projects/Vala/PangoCairoSample
• https://www.cairographics.org/cookbook/pycairo_pango/
• http://jcoppens.com/soft/howto/pygtk/pangocairo.en.php
• https://www.programcreek.com/python/example/58134/pangocairo.CairoContext
• https://www.roxlu.com/2014/046/rendering-text-with-pango--cairo-and-freetype