Changes:
- #997: Release libs v1.4.0-preview3
- #996: Bump up lib versions
- #994: Retrieve format property during V2 serialization
- #991: Bump Microsoft.NET.Test.Sdk from 17.3.0 to 17.3.1
- #988: Attach changelog labels for improved release notes experience
- #987: Cater for file content transferred with base64 encoding
- #985: Compute hash of OpenApi document
- #984: Bump Verify.Xunit from 17.10.0 to 17.10.2
- #979: Release v1.4.0-preview2
- #958: Release Libs v1.4.0-preview1