App Configuration Readme and Samples issues

[v-xuto]

Section Link:

Suggestion:
1).Add hyperlink for Microsoft Open Source Code of Conduct https://opensource.microsoft.com/codeofconduct/
2).Add hyperlink for Code of Conduct FAQ https://opensource.microsoft.com/codeofconduct/faq/

Section Link1, link2:

Reason:
TypeError: request() got an unexpected keyword argument 'keys'.

Suggestion:
Update to: items = client.list_revisions(key_filter="MyKey")

@jongio for notification.

[xiangyan99]

Fixed