chore: release 0.4.0

[github-actions]

🤖 I have created a release *beep* *boop*

0.4.0 (2021-10-26)

Features

• add agribalyse score to EcoscoreData (#160) (4565f73)
• add ecoscoreData.missingDataWarning field support (e1ccb26)

Bug Fixes

• add carbohydratesUnit and fatUnit in the Nutriments class (8020b38)
• address path warning in example/pubspec.yaml (1a8e415)
• clean up imports (41af6dd)
• Delete release.yml + added needed package to pubspec (#280) (a0f5c7c)
• failing test (b256809)
• improve error messages when saving products (e5f766d), closes #247
• make tests pass (695c4cd)
• no user is required when searching products (136c7ed)
• Nutriments JSON conversion bug related to micro gram unit (#267) (9123647), closes #265
• relax and correct test assertions (#266) (bde86da)
• remove unused dependency, async_loader (08d2d75)
• test assertions (ea9ef50)
• test instructions (6a339c9)
• tweak handling of status codes based on PR feedback (0324b91)
• update expected test results. (79714c3), closes #146
• write API for nutrient units (3339810), closes #224

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