Validate label size

[kamilturek]

As per Labelary docs, the maximum label size is 15 x 15 inches.

Maximum label size of 15 x 15 inches. Larger labels result in a HTTP 400 (Bad Request) error.

Validation can be added to these functions.

go-zpl/zpl.go

Lines 109 to 123 in ff042c3

	func WithWidth(width int) option {
	return func(c *converter) error {
	c.width = width
	return nil
	}
	}
	func WithHeight(height int) option {
	return func(c *converter) error {
	c.height = height
	return nil
	}
	}