Fix for custom view tasks

[kevinleung23]

Fixes # N/A

Proposed Changes

The current examples do not work as the validDomains property in the Microsoft Teams manifest are missing. All other components of the messaging extension sample work other than the "Web View" and "Static HTML" options as they both require a fetch task.

• Adding the required property to both JS and Python samples
  • Opted to include an ngrok wildcard as that is the technology suggested by the sample README

Testing

• No new tests added. Sample now works out of the box