Add more complex examples

The existing examples are great to get started with simple projects, but are not enough for more complex projects:
- cmake/autotools/meson projects with multiple targets (e.g mpg123, vorbis, etc.).
- According to https://docs.conan.io/en/latest/migrating_to_2.0/recipes.html#the-scm-attribute the scm attribute was removed but [Git ](https://docs.conan.io/en/latest/reference/conanfile/tools/scm/git.html#conan-tools-scm-git) seems to be missing a few features like `"submodule": "shallow",` `"shallow": True,` scm attributes. Again, a more complex example will be more than welcome.