add scale, chord and tuning

[sugizo]

already discussed on https://github.com/cheap-glitch/fretboarder/issues/8 https://github.com/cheap-glitch/fretboarder/issues/9 https://github.com/cheap-glitch/fretboarder/issues/10

step for PR

cd fretboarder
git remote -v
git remote add upstream https://github.com/cheap-glitch/fretboarder.git
git remote -v
git fetch upstream
git checkout develop
git merge upstream/develop
git checkout -b scale_chord_tuning
git checkout scale_chord_tuning
git add --all
git commit -am "add scale, chord and tuning"
git push origin scale_chord_tuning
open https://github.com/cheap-glitch/fretboarder

thanks

[cheap-glitch]

First of all, thank you a lot for this contribution! 👍 I merged this across three different commits: one for the scales, one for the arpeggios and one for the tunings & instruments (5fbefee, 91b1d69 and f203ae9 respectively) and credited you as co-author each time.

In the future, when you open PRs to contribute to projects, you should try to split them into small, self-contained units. Ideally you should open one PR for each issue (so three PRs in this case). That way it's much easier for the maintainer to apply the changes incrementally, by picking each one, reviewing it and merging it before moving to the next. At the very least you should have split this PR into three commits, e.g. by using git add -p to split the modifications to music.js into three (or more) commits.