Missing the step of running `az login` before running az commands

[Menghua1]

Describe:
Copying and running the az command from the UI in the terminal to get the func app key fails because Azure CLI is not logged in. The detailed error message is as follows:

Repro Steps:

1. Create a Codespace/Open a Devcontainer.
2. Run azd auth login.
3. Run azd env set CI true.
4. Run azd up.
5. Copy and run the az command from the UI in the terminal.

Environment:

• OS: Codespace, Devcontainer and Windows locally.
• Azd version: azd version 1.18.2 (commit a7b2bdc861f0616438327854f11169a08fdfec96).

Expected behavior:
The az command can be run successfully.

Suggestion:
Add the step az login before running az commands in the Readme.md.

@JayChase and @hemarina for notification.