Add loop to HookOptions

[Rikthepixel]

After using this library myself and needing to loop a sound, I discovered that Howler exposes an option for looping sounds. We can already use this through delegated in HookOptions.

After looking through some of the issues, there seems to be some confusion around how to loop sounds. This PR solves that
confusion by making the following changes.

Changes

• Adding a boolean property loop to HookOptions
• Adding documentation for said loop property
• Updating the loop property on sound in useEffect
• Added volta to package.json to support Volta (a Node version manager)

Closes issues

• Is it possible to play the sound on repeat? #137

[channprj]

@joshwcomeau I think this is good idea. Would you please review ths PR? 🙏🏻