Add help topic about installing site from configuration

Problem/Motivation

In 📌 Fix up minor copy problems in help topics Fixed , there is this item:

• core.config_overview.html.twig -- alexpott wrote on #3095734-102: Convert config module hook_help() to topic(s) → (slightly edited for clarity): We need to add information about installing from configuration, as the part on cloning could encompass this. If people knew about and used installing from configuration more often then people wouldn't think so much about the site UUID.

Which is part of a host of other minor issues with help topics. Moving this task to its own issue so that it can be worked on and discussed in a manageable way.

Steps to reproduce

Proposed resolution

1. Update core.config_overview.html.twig with a brief note about how it's possible to install a site from configuration.
2. Add a new topic with steps for installing a site from configuration.
3. Add the new topic to the frontmatter's related list in core.config_overview.html.twig.

Note: Help Topics is being merged with the core Help module and help topics will be eventually moved to their own modules, so the locations of these files may shift.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet