Add EditorConfig `.editorconfig` to project

Summary of the new feature

Add EditorConfig .editorconfig to the project, like other PowerShell related repos already have.

• https://github.com/PowerShell/PowerShell/blob/master/.editorconfig
• https://github.com/PowerShell/PSResourceGet/blob/master/.editorconfig
• https://github.com/PowerShell/vscode-powershell/blob/main/.editorconfig

Proposed technical implementation details (optional)

Unify style, syntax, rules, linting, formatting across PowerShell related projects.

What is the latest version of PSScriptAnalyzer at the point of writing

Not relevant.

首先比较 PowerShell、PSResourceGet 和 vscode-powershell 中链接的 .editorconfig 文件。在项目根目录添加一个包含适用于 PSScriptAnalyzer 的规则的 .editorconfig；当项目具有与相关仓库一致的统一配置时，即视为完成。