Related to microsoft/OpenAPI.NET.OData#129 and microsoft/OpenAPI.NET.OData#141

/$count returns a text/plain response with an int32. It can't be changed to another type due to how the OData protocol is designed

To fully support this (once the conversion pull request gets merged), we need to:

• update the builder so it generates fluent API paths for text/plain as well
• add deserialization libraries for text/plain for C#, TS, Java, Ruby, Go (and eventually PhP)
• register these providers by default
• update the readme to point to these new libraries