Migrate to .Net 6.0

Migrate Easify.Notifications to .Net 6.0 (#6)

* [DEV-1929] Upgraded to .net 6

* [DEV-1929] Namespace and global using updates

* [DEV-1929] Updated ci.yaml

* [DEV-1929] Added global system usings file

* [DEV-1929] Update to release.yaml file

* [DEV-1929] Upgraded all NetStandard projects to Net 6

* [DEV-1929] Small usings file tidy up

Upgrade to the Net 5.0

V5.0.1

Update README.md

Merge to main

Update release.yml

Correct release.yml