Allow script import to add action handler to canned response

[jeffm2001]

Description

Found a stray branch I meant to create a PR for 2 years ago. This updates the Google Doc script importer to allow you to use action handlers on canned responses in addition to tags.

I also updated the template script linked in the HOTWTO file to reflect this: https://docs.google.com/document/d/1gFji2Vh_0svb4j7VUtmJZkqNhRWt3htp_bdGoWh6S6w/edit#heading=h.fo6nvxcomzft

Checklist:

• I have manually tested my changes on desktop and mobile
• The test suite passes locally with my changes
• If my change is a UI change, I have attached a screenshot to the description section of this pull request
• My change is 300 lines of code or less, or has a documented reason in the description why it’s longer
• I have made any necessary changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• My PR is labeled [WIP] if it is in progress