feat: support Next <10.0.6 users with Essential Next.js plugin

[ehmicky]

See https://github.com/netlify/next-on-netlify-enterprise/issues/16#issuecomment-791541482

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• Read and followed the plugin author guidelines.
• Included all required fields in your entry.
• Tested the plugin locally and on Netlify, using the plugin version stated in your entry.

[lindsaylevine]

ty!!! <3