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.

先比較 PowerShell、PSResourceGet 和 vscode-powershell 中連結的 .editorconfig 檔案。在專案根目錄新增一個包含適用於 PSScriptAnalyzer 的規則的 .editorconfig；當專案具有與相關儲存庫一致的統一設定時，即表示完成。