Mention lsp-powershell, an Emacs lsp-mode client that leverage PowerShellEditorServices (#982)

Author: kiennq

README.md

@@ -17,6 +17,7 @@ The functionality in PowerShell Editor Services is already available in the foll
 - [The VSCode PowerShell extension](https://github.com/PowerShell/vscode-powershell), also available in Azure Data Studio
 - [coc-powershell](https://github.com/yatli/coc-powershell), a vim/neovim PowerShell plugin
 - [The IntelliJ PowerShell plugin](https://github.com/ant-druha/intellij-powershell)
+- [lsp-powershell](https://github.com/kiennq/lsp-powershell), an Emacs PowerShell plugin
 
 ## Features