feat: Migrates elevation-simple to js-api-samples.

[willum070]

This PR does the following things:

• Migrates elevation-simple to js-api-samples.
• Updates the sample to use gmp-map-3d.

[snippet-bot]

Here is the summary of changes.

You are about to add 3 region tags.

• samples/elevation-simple/index.html:7, tag maps_elevation_simple
• samples/elevation-simple/index.ts:7, tag maps_elevation_simple
• samples/elevation-simple/style.css:6, tag maps_elevation_simple

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