Use the keyring python module with gnome-keyring

Not exactly a bug, but a lack of documentation. Sorry if it is not the right use of keyring.

In a shell script I can get a needed password from gnome-keyring to a variable or feed it via pipe to some program:
```
passwd=$(secret-tool lookup user myname domain somehost.com)
```

If I got it right, keyring can be used for the same purpose in a python script. I could not find any minimal working example example to do that in python with keyring module. There probably must be a better way than using `os.popen(cmd).read()` with the above shell command...

The example from the README file
```
$ python
>>> import keyring
>>> keyring.get_keyring()

>>> keyring.set_password("system", "username", "password")
>>> keyring.get_password("system", "username")
```
launces "KDE Wallet Service" configuration which is not relevant for me, since I use gnome-keyring...

Thank you!

**Environment**

- OS: Ubuntu 22.04

```
$ dpkg -l |grep python3-keyring
ii python3-keyring 23.5.0-1 all store and access your passwords safely
$ keyring --list-backends
keyring.backends.kwallet.DBusKeyring (priority: 4.9)
keyring.backends.fail.Keyring (priority: 0)
keyring.backends.chainer.ChainerBackend (priority: 10)
keyring.backends.libsecret.Keyring (priority: 4.8)
```

Start with the existing Python examples in README and the reported `secret-tool` usage for gnome-keyring. Verify how the keyring module selects the libsecret backend in the listed Ubuntu environment, then document a minimal Python example and the relevant backend configuration so the README clearly covers gnome-keyring.

Written by the indexing model from the issue text.