Only use pwsh.exe if it is installed!

[mgrosser3]

• Currently the configuration will be failed, if PowerShell 7 is not installed

:!ls shell failed to start: no such file or directory: pwsh.exe Shell beendet -1

• IF pwsh.exe IS FOUND

  • vim.opt.shell = 'pwsh.exe'

• ELSE

  • vim.opt.shell = 'powershell.exe'