Add single option radio button example

[jakeroseman]

Add basic radio button example to serve the CUJ "Show a single select option to my users."

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• compose/snippets/src/main/java/com/example/compose/snippets/components/RadioButton.kt:38, tag android_compose_components_radiobuttonsingleselection

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[JolandaVerhoef]

you probably don't want to check this file in