Documentation: How to configure and enable basic LDAP/AD User Authentication for Oncall

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I was having trouble getting basic LDAP/Active Directory authentication enabled in my instance of Oncall due to the config options provided. In the end I figured out that all that is needed is to enable the following:

- Enable `module: 'oncall.auth.modules.ldap_example'`
- Enable and configure `ldap_url`
- Enable and configure `ldap_user_suffix`
- Enable and configure `ldap_cert_path`

Here is a proper example:
```
# Example configuration for LDAP-based auth
module: 'oncall.auth.modules.ldap_example'
ldap_url: 'ldaps://my.domain.com'
ldap_user_suffix: '@my.domain.com'
ldap_cert_path: '/home/oncall/configs/corp_cert.pem'
```
Everything else in the module config block should be commented out.

All of the other configs including `ldap_bind_user`, `ldap_bind_password`, `ldap_base_dn`, and `ldap_search_filter` wasn't needed as I assume they are used by the `ldap_import` module.

Is it recommended to submit a PR to add notes on separating out the different module options in the config.yaml? If not, what is the best way to submit contributions to the official documentation at https://oncall.tools/docs/ (documentation is hosted on read the docs)?

Start with the LDAP module options in config.yaml and the documentation at https://oncall.tools/docs/. Compare the ldap_example settings with the ldap_import options, then document which settings are required for basic LDAP/AD authentication and how documentation contributions are submitted. Done means the two module configurations are clearly separated and the contribution path is explained.

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