chore: release 4.0.0

[github-actions]

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

4.0.0 (2020-10-07)

⚠ BREAKING CHANGES

• event: make the event's time property only a string (src(event)!: make the event's time property only a string cloudevents/sdk-javascript#330)

Features

• add a constructor parameter for loose validation (#328) (1fa3a05)
• add emitterFactory and friends (#342) (e334b6e)
• introduce Message, Serializer, Deserializer and Binding interfaces (#324) (f3953a9)

Bug Fixes

• do not alter an event's data attribute (#344) (1446898)
• extend Node.js IncomingHttpHeaders in our Headers type (#346) (f6be285)
• package.json & package-lock.json to reduce vulnerabilities (#338) (eca43d9)
• upgrade cloudevents from 3.0.1 to 3.1.0 (#335) (7423acb)

Tests

• implement pending tests leftover from TS rewrite (#315) (b5cf886)

Miscellaneous

• add an automated GH action for releases (#329) (a9114b7)
• update release please to the latest release(2.4.1) (#345) (76688c4)
• event: make the event's time property only a string (#330) (6cd310c)
• example: Replaced body parser with express JSON parser (#334) (4779d89)
• add cucumber.js to list of files to lint and /docs to .gitignore (#327) (17d4bc8)
• Remove commented version import. (#319) (0adcc35)
• typo (#313) (81623ac)
• Update README with correct links for the support specification versions (#321) (73f0bec), closes #320
• Update references of master to main (#316) (4bf2eb8)
• validate cloudevent version agnostic (#311) (8ac3eb0)

Documentation

• update README with latest API changes (#347) (138de37)
• update README with maintainer names (#337) (0a12146)

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