Add snippet for screenshot test

[kul3r4]

Add a snippet for the Wear Screenshot test

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• wear/src/test/java/com/example/wear/snippets/m3/list/ListTest.kt:26, tag android_wear_screenshot_test

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[ithinkihaveacat]

Nice! Good to get this in.