Breaking changes: scoping the npm package and dropping Node.js < 10 support (RFC for MDN Data 3.0)

[ExE-Boss]

Summary

MDN Data should make a couple of breaking changes:

• move the package into the @mdn scope on npm (i.e., rename mdn-data to @mdn/data)
• drop support for Node.js < 10.

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See mdn/browser-compat-data#6640 for details.