Update README.md to include auth login fix for github codespaces users

[GiuseppeGalilei]

Purpose

Proposes an alternative command for azure auth login that solves issues encountered by GitHub Codespaces users.
Closes #1855

Does this introduce a breaking change?

When developers merge from main and run the server, azd up, or azd deploy, will this produce an error?

[ ] Yes
[x] No

Does this require changes to learn.microsoft.com docs?

This repository is referenced by this tutorial
which includes deployment, settings and usage instructions. If text or screenshot need to change in the tutorial,
check the box below and notify the tutorial author. A Microsoft employee can do this for you if you're an external contributor.

[x] Yes
[ ] No

Type of change

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[x] Documentation content changes
[ ] Other... Please describe:

Code quality checklist

See CONTRIBUTING.md for more details.

• The current tests all pass (python -m pytest).
• I added tests that prove my fix is effective or that my feature works
• I ran python -m pytest --cov to verify 100% coverage of added lines
• I ran python -m mypy to check for type errors
• I either used the pre-commit hooks or ran ruff and black manually on my code.

[github-actions]

Check Broken Paths

We have automatically detected the following broken relative paths in your files.
Review and fix the paths to resolve this issue.

Check the file paths and associated broken paths inside them. For more details, check our Contributing Guide.

File Full Path	Issues
README.md	# Link Line Number 1 /docs/gpt4vision.md 44
samples/chat/README.md	# Link Line Number 1 /docs/gpt4vision.md 60

[github-actions]

Check Broken Paths

We have automatically detected the following broken relative paths in your files.
Review and fix the paths to resolve this issue.

Check the file paths and associated broken paths inside them. For more details, check our Contributing Guide.

File Full Path	Issues
README.md	# Link Line Number 1 /docs/gpt4vision.md 44
samples/chat/README.md	# Link Line Number 1 /docs/gpt4vision.md 60

[pamelafox]

Technically azd is supposed to autodetect when to use device code, but I just got another report of it not working, so I think we should go ahead and document.