Depend on script dependencies for downstream webpack

Downstream webpack will need any dependencies src/ depends on so it can
successfully build. Also if multiple packages being built into a larger
script share a common dependency version range, they can share the
dependency instead of duplicating it. This will save built file size,
execution time, and memory.

webpack.config.js

@@ -20,5 +20,10 @@ module.exports = {
                 presets: ['es2015']
             }
         }]
+    },
+    externals: {
+        'audio-context': true,
+        'minilog': true,
+        'startaudiocontext': true
     }
 };