Add proverb

[BNAndras]

No description provided.

[glennj]

Perhaps a multi-line string for the long ones?

Suggested change

	final expected =
	"For want of a nail the shoe was lost.\nFor want of a shoe the horse was lost.\nFor want of a horse the rider was lost.\nFor want of a rider the message was lost.\nFor want of a message the battle was lost.\nFor want of a battle the kingdom was lost.\nAnd all for the want of a nail.";
	final expected = '''
	For want of a nail the shoe was lost.
	For want of a shoe the horse was lost.
	For want of a horse the rider was lost.
	For want of a rider the message was lost.
	For want of a message the battle was lost.
	For want of a battle the kingdom was lost.
	And all for the want of a nail.''';