addButton & setRangeValue functions

[kabrio]

Just a simple wrapper around quicksettings to be able to add buttons by calling addButton(title, function).
Also wrapped setRangeValue function from quicksettings to enable scripted value changes of sliders.
See button-setRangeValue example for demonstration.

[micahwalter]

Would be nice to see this merged...

[craftoid]

Hey @kabrio —thanks for your pull request, I finally got back to work on p5.gui.
I have rewritten it quite a bit, but I will try to incorporate your suggestions / changes.

[craftoid]

1. Adding Buttons and HTML is definitely on my list... But I'd rather create those auto-magically from functions and DOM elements.
2. In general p5.gui should magically reflect changes of the variables passed to it.
   So rather than scripting changes to the GUI, the gui should watch the variables and update accordingly...
3. I like your randomize example a lot 👍
   I will adapt it to fit the approach outlined above

Thanks for your contribution, and sorry for the long delay!

[Catz1301]

Extremely annoying to check the differences between the files. It's generally a good idea to only change what needs to be changed, and do not convert line endings before committing (unless GitHub automatically handles line endings).