chore: release 4.0.0-beta.0 (#701)

* chore: release 4.0.0-beta.0

* Apply suggestions from code review

Co-authored-by: token-generator-app[bot] <82042599+token-generator-app[bot]@users.noreply.github.com>
Co-authored-by: Matt Kane <[email protected]>

Author: token-generator-app[bot]

Diff for: CHANGELOG.md

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+# Changelog
+
+## [4.0.0-beta.0](https://www.github.com/netlify/netlify-plugin-nextjs/compare/v3.9.1...v4.0.0-beta.0) (2021-10-15)
+
+
+A complete rewrite of the Essential Next plugin. See the README for details and migration instructions