This commit adds to the RTD the links references to source code
examples.
The examples are added to TUF ngclient Updater, Metadata and API
reference.
includes a seed for examples/README.md
Signed-off-by: Kairo de Araujo <kdearaujo@vmware.com>
Instead of having duplicate metadata in examples/ and tests/repository_data, retain only the metadata in tests/repository_data and link to them from METADATA.md