Add powershell instructions, fixes #8883

doc/00-intro.md

@@ -134,10 +134,18 @@ to download `composer.phar`.
 
 Create a new `composer.bat` file alongside `composer.phar`:
 
+Using cmd.exe:
+
 ```sh
 C:\bin> echo @php "%~dp0composer.phar" %*>composer.bat
 ```
 
+Using PowerShell:
+
+```sh
+PS C:\bin> Set-Content composer.bat '@php "%~dp0composer.phar" %*'
+```
+
 Add the directory to your PATH environment variable if it isn't already.
 For information on changing your PATH variable, please see
 [this article](https://www.computerhope.com/issues/ch000549.htm) and/or