Update Sample Readme's to include a PShell Script let to set up appsettings for C# projects

[MattB-msft]

Ref:
Consider using the same approach as in nodejs, providing a manifest.template.json with a helper script to replace the values:

Agents/samples/complex/copilotstudio-skill/nodejs/README.md

Lines 51 to 56 in d4b26c8

	Replace Manifest Values
	```ps
	$url='{tunnelUrl}'
	$clientId='{clientId}'
	(Get-Content public/manifest.template.json).Replace('{baseUrl}', $url).Replace('{clientId}', $clientId) | Set-Content public/manifest.json