Az-account-switcher

After installing the package, the cli should work without extra dependencies.

Changes:
- Add dependency to 'azure-cli-core'.

Another release to see Github actions in action.

Changes:
- Improve the help text.

Test releasing using Github Actions automatically to PyPi.

Changes:
- Add optional argument `-n` to directly switch accounts.
- Drop 3.5 support, which is in line with the Azure CLI.