Add linting rule

[zhiyuanliang-ms]

Why this PR?

Add code format check

Visible changes

Linting rules are defined in .editorconfig file.

property is added to the csproj file and then all code format issues will be reported during build process. In the editorconfig file, it sets the severity of IDE0055 and some other formating rules to error.
This will make build fail if the formating rule is not followed.

[juniwang]

what's the purpose of this file: https://github.com/Azure/AppConfiguration-DotnetProvider/blob/main/AzureAppConfigurationRules.ruleset ?

[zhiyuanliang-ms]

what's the purpose of this file: https://github.com/Azure/AppConfiguration-DotnetProvider/blob/main/AzureAppConfigurationRules.ruleset ?

@juniwang This file is used for enforce CA2007 check. #410

Code analysis is a big topic. It includes two aspects: code quality and code style.

CA2007 belongs to code quality check.

Even for code style, there are 4 aspects as shown in the screenshot below.

In this PR, we only focus on the formatting rules.

[juniwang]

what's the purpose of this file: https://github.com/Azure/AppConfiguration-DotnetProvider/blob/main/AzureAppConfigurationRules.ruleset ?

@juniwang This file is used for enforce CA2007 check. #410

Code analysis is a big topic. It includes two aspects: code quality and code style.

CA2007 belongs to code quality check.

Even for code style, there are 4 aspects as shown in the screenshot below.

In this PR, we only focus on the formatting rules.

OK,