Update bibliography in help file

[LegalizeAdulthood]

The most recent books listed are from 1991

[LegalizeAdulthood]

Things to add:

• Gerald A. Edgar, "Classics On Fractals"
• Kenneth Falconer, "Fractal Geometry: Mathematical Foundations and Applications"

possibly:

• Michael Frame, "Fractal Worlds: Grown, Built, and Imagined"