Note in README about relative weights (modality & regularizer)

[Alvant]

Worth to note that relative weights are cool and library provides simple ways to use it.

• More intuitive way to choose modality weights (not just some random values virtually out of nowhere)
• Cubes use relative weights by default: so the recommended range for regularizer weights is between 0 and 1, not ~10000 (but other values also possible)

Related: #62