Add instructions in README on how to edit demo

[joshdholtz]

Not sure if it has just been a long week but I'm struggling to get the demo iOS project to update rebuild a framework of my changes 😬

It looks like it is looking for the Few.framework in a build/Debug-iphoneos directory but that does not exist. I have tried building/running/archiving the framework targets and no frameworks get put there. Is there something I am missing?

[joshaber]

Are you trying to rebuild the framework itself, or one of the demo projects?

[joshdholtz]

I was working on adding a fun new feature to Few.Element and I wanted to test it in the demo project. The demo project looks like it relies on a built Few.framework in the build/Debug-iphoneos directory. It didn't seem like my change to Few.Element was being reflect in the demo app but I may have been an idiot 😬 I will double check to make sure I was actually doing things right.

[joshaber]

Ah, sorry about that! It looks like it was trying to link to the Carthage-built version before. It should be fine now.

[joshdholtz]

Yesssssss, thank you! Expect more PRs from me 😊