The sections on FetchContent's FIND_PACKAGE_ARGS and on
Dependency Providers only apply to CMake 3.24+, so add
versionadded markers at the start of both sections.
The guide previously only focused on the find_package() command,
with a bias towards libraries. FetchContent was not mentioned at all.
Reorganise and update the existing content. Add new sections to cover
providing dependencies with FetchContent and dependency providers.
Improve discoverability of the guide by mentioning it at the beginning
of the find_package(), FetchContent and dependency provider docs.
* Move sections to be same level as Introduction in "Using Dependecies"
* Rename "Importing Exporting Targets" to "Importing Exporting Guide"
* Add an Introduction header to the Tutorial and Importing Exporting Guide
Add some prose to the documentation index page to guide readers to the
major manuals and guides.
Add a new "User Interaction Guide" to help the class of new user
who wishes to build a project with CMake for the first time, such as
after cloning a repo from a git repository.
Add a new "Using Dependencies Guide" to help the class of new
user who wishes to consume a SDK provided by a third party and needs a
starting point. This is a different type of user to the user who wishes
to create their own project from scratch (addressed by the
`cmake-buildsystem(7)` manual) as each will encounter needs for
information discovery in a different order.
