Add 3d-clamp-mode sample

[oppenheimera]

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[snippet-bot]

Here is the summary of changes.

You are about to add 3 region tags.

• samples/3d-clamp-mode/index.html:7, tag maps_3d_clamp_mode
• samples/3d-clamp-mode/index.ts:8, tag maps_3d_clamp_mode
• samples/3d-clamp-mode/style.css:6, tag maps_3d_clamp_mode

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