Improve documentation of german notation and useful conversions in supercollider with ctk library (which are amazing!!)

[pedro-nonfree]

This ticket is open to accomplish the effort of improving/showing documentation of:

• basic music notation:
  • german notation c d e (or cn, dn, en), where:
    • f sharp is es
    • e flat is ef
• methods:
  • .hertz: from notes to frequency
  • .keynum: from notes to midi notes
  • .note
    • .note from midi to notes
    • .note(true) from frequency to notes

History: So I was looking for help expressing the notes in a more musical-traditional sense with supercollider and thanks to @joshpar he guided me to get into it.

an example:

(
p = Pbind(
        // german notation notes, converted to midi
	\midinote, Pseq(['c3', 'c3', 'ef3', 'c3', 'g3', 'fs3'].keynum, inf),
        // rhythmic values
    \dur, Pseq([1, 0.5, 0.5, 1, 1] * 0.6, inf)
).play;
)