Add function url to cloud_function templalte outputs

[ozydingo]

While it's simple enough to describe the function later, it is helpful to simply include the function URL in the template outputs.

Example result:

OUTPUTS          VALUE
function-output  {"hello":"world","time":"2020-02-09T16:12:42.253Z","codeHash":"b70b788b5dd0af98ba801b3eb60975a9"}
function-code    gs://playground-deploy-artifacts/b70b788b5dd0af98ba801b3eb60975a9.zip
function-url     https://us-central1-playground-252414.cloudfunctions.net/deploy-functioncf

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[ozydingo]

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