Completely remove envify in favor of loose-envify

[autra]

Following the discussion in #203, this PR move loose-envify from dependencies to devDependencies.

I also took the opportunity to choose loose-envify over envify everywhere, as they are doing the same thing anyway. I have no opinion whether loose-envify is better than envify or not. Using yarn run test does not show any measurable difference in term of execution time, so I can switch back to envify if you prefer.

Closes #203.

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[autra]

We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file.

Oh yes. Should be ok now :-)

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[ljharb]

loose-envify's gotchas don't apply here, since we're not using env values in template literals, nor as anything but direct literal member access, so this seems fine.

[autra]

Thanks!