Update dotnet coding standards with code analysis rules

[shreyanshJain852]

Update dotnet coding standards with code analysis rules.

• Added different editor configs for .NET Core and Framework
• .NET Core contains the configured CA rules and the rest will be treated by .NET SDK as per default severity
• .NET Framework contains the configured CA rules as well as the rest of the rules with warning severity
• Include section for setting up configurable maintainability CA rules
• Configured md file to have collapsible accordion for the editor config