Add doc regarding how to add dict fields to config.

Documentation/SwiftBundler.docc/configuration.md

@@ -21,8 +21,12 @@ icon = "icon.png"
 prebuild_script = "./utils/prebuild.sh"
 postbuild_script = "./utils/postbuild.sh"
 
-[apps.HelloWorld.extra_plist_entries]
+[apps.HelloWorld.plist]
 commit = "{COMMIT_HASH}" # This could be any key-value pair, 'commit' is just an example
+CFBundleURLTypes = [ { type = "dict", value = { CFBundleTypeRole = 'Viewer', CFBundleURLName = 'HelloWorld', CFBundleURLSchemes = [ 'helloworld' ] } } ]
+# You can also define many other kinds of platform-specific fields, as an example, above is
+# how you would specify a list of URL schemes (http, ftp, and so on) supported by the app,
+# in this example, to allow opening your app from the URL: (ex. helloworld://open)
 ```
 
 > Note: Only the `product` and `version` fields are required.