Updated azure web app deploy command to allow a slot to be specified …

[Stefanie899]

…to which the app should be deployed.

• [NA] Related GitHub issue(s) linked in PR description
• [x] Destination branch merged, built and tested with your changes
• [x] Code formatted and follows best practices and patterns
• [x] Code builds cleanly (no additional warnings or errors)
• [x] Manually tested
• [x] Automated tests are passing
• [x] No decreases in automated test coverage
• [x] Documentation updated (readme, docs, comments, etc.)
• [x] Localization: No hard-coded error messages in code files (minimally in string constants)