Update final release version 4.0.0

[tanaynigam]

Description

One Line Summary

Update project version to 4.0.0

Details

Update project and nuspec file to final release version 4.0.0

Motivation

Update project and nuspec file to final release version 4.0.0 and updated information in the nuspec file

Scope

• Update project files to final release version 4.0.0
• Update nuspec file to final release version 4.0.0
• Update author in nuspec file to OneSignal
• Update icon in nuspec file

Affected code checklist

• [ ] Notifications
  • [ ] Display
  • [ ] Open
  • [ ] Push Processing
  • [ ] Confirm Deliveries
• [ ] Outcomes
• [ ] Sessions
• [ ] In-App Messaging
• [ ] REST API requests
• [ ] Public API changes

Checklist

Overview

• [x] I have filled out all REQUIRED sections above
• [ ] PR does one thing
  • If it is hard to explain how any codes changes are related to each other then it most likely needs to be more than one PR
• [ ] Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• [ ] I have included test coverage for these changes, or explained why they are not needed
• [ ] All automated tests pass, or I explained why that is not possible
• [ ] I have personally tested this on my device, or explained why that is not possible

Final pass

• [x] Code is as readable as possible.
  • Simplify with less code, followed by splitting up code into well named functions and variables, followed by adding comments to the code.
• [x] I have reviewed this PR myself, ensuring it meets each checklist item
  • WIP (Work In Progress) is ok, but explain what is still in progress and what you would like feedback on. Start the PR title with "WIP" to indicate this.

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