add async methods to read a reqif file

[samatstariongroup]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of the ReqIFSharp
• I have searched open and closed issues to ensure it has not already been reported

Description

The current implementation is synchronous, the API should be mirrored adding asynchronous methods on the API using the async methods of the XML reader

Steps to Reproduce

NA

System Configuration

• ReqIFSharp version:
  • ReqIFSharp: 4.0.0

[samatstariongroup]

after some reading on xml serialization docs, seems this is not possible. So, will not be implemented until I better understand whether this is possible etc.