We decided to split the media webpack config into it's own file. The
main webpack config then combines this file with the packages config.
Include vendor scripts by copying them. We copy the minified files if
they are available. If they aren't available we minify the original
files ourselves.
Props omarreiss, herregroen, gziolo, youknowriad, netweb, adamsilverstein.
Merges [43719] to trunk.
See #45065.
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git-svn-id: http://core.svn.wordpress.org/trunk@43942 1a063a9b-81f0-0310-95a4-ce76da25c4cd
