Fix typo

Author: onyxmaster

README.md

@@ -3,4 +3,4 @@
 [![NuGet version (StructuredFieldValues)](https://img.shields.io/nuget/v/StructuredFieldValues)](https://www.nuget.org/packages/StructuredFieldValues/)
 
 This is a .NET parser for Structured Field Values for HTTP, compliant with [RFC 8941](https://httpwg.org/specs/rfc8941.html).
-Its correctness is ensured the [test suite](https://github.com/httpwg/structured-field-tests) from IETF HTTP Working Group.
+Its correctness is ensured by the [test suite](https://github.com/httpwg/structured-field-tests) from IETF HTTP Working Group.