[docsprint] map.on additional suggestions

[colleenmcginnis]

Ref #9560

ℹ️ This PR is part of a larger effort to improve generated API documentation. It targets the docsprint-ds-map-on branch, which will merge into the major feature branch for this work.

@danswick I decided to commit my suggestions separately as to not mess up your branch if you disagree with my suggestions. 💁‍♀️ My suggestions include:

• Adding a second example when the layerId param is optional.
• Adding **Note:** when the layerId param is optional.
• Adding **Important:** when the layerId param is required.
• Attempting to clarify the difference between mouseover and mousemove, which are currently described using the same language. (We might need some clarification from @asheemmamoowala on this.)

cc @katydecorah

[danswick]

excellent suggestions! i screwed up the order of events in The Great Merging, so I cherry picked your commit over to the doscprint branch: #9607.