rotate icon in animate a point along a route example

[andrewharvey]

Launch Checklist

• briefly describe the changes in this PR

closes #4767 by rotating the icon along the route

• n/a write tests for all new functionality
• n/a document any changes to public APIs
• n/a post benchmark scores
• manually test the debug page

[andrewharvey]

I see a trend here... all three open PRs targeting mb-pages are stuck with CI saying "Expected — Waiting for status to be reported".

[jfirebaugh]

Thanks Andrew!

I updated the branch settings so that only the appropriate builds are required -- so you should be able to merge all the mb-pages PRs once approved.

[jfirebaugh]

Replace the function with ["get", "bearing"]. (We decided to always use expressions in examples.)