Refactoring sample code to match README and provide output on errors … …for V4 (#9) * Update v4 and README.md according to PR * Modified README.md * Change 'web app' to uppercase in README.md * Change secret name and secret value to custom name and value, update v4 * Update README.md * Update README.md Co-authored-by: Fred Gao (MSFT) <v-yicgao@microsoft.com>