Add reactR colorpicker input example

[alandipert]

This adds a reactR-based colorpicker example for showcase on https://github.com/rstudio/blog/pull/168

It was extracted from http://github.com/react-R/colorpicker-example

[wch]

Just checking: this should just work in the Docker container without installing anything extra, right?

Also it would be good to edit the comment here to mention this app as well:

shiny-examples/install_deps.R

Lines 62 to 63 in 44e38a8

	# For 150-reactr-input
	"react-R/reactR",

[alandipert]

It should work without anything extra. And thanks for pointing out that line in install_deps.R, it can actually be removed now that reactR 0.4.0 is on CRAN.

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