Add prepare script

[couac]

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[daffl]

Thank you @couac. I will merge this PR, I should note though that:

• feathers-hooks will become core of the next Feathers release (see https://blog.feathersjs.com/after-auk-whats-next-for-feathers-buzzard-c68358a3e62f)
• We will be removing the compilation steps for all plugins exactly for the reason you mentioned (see Remove Babel Compilation - Drop Support For Node v4 feathersjs/feathers#608)