docs(messaging): add syntax highlighting to additional code blocks

[hendrickson-tyler]

Checklist

• Issue number for this PR: No issue, can create one if required
• Docs included?: Yes
• Test units included?: Not applicable
• In a clean directory, yarn install, yarn test run successfully? Yes

Description

A few code blocks on the Cloud Messaging docs did not define the language, so syntax highlighting was missing. This simply defines ts so that syntax highlighting works.

[hendrickson-tyler]

Closing as a duplicate of #3627