added example loading key created with in-toto-keygen

[ashutoshsao]

i have made a text file named examplefile.txt, then used the command in-toto-keygen -t rsa -b 4096 examplefile.txt , it created 2 files { examplefile.txt, examplefile.txt.pub },i have uploaded the first file examplefile.txt after renaming it as Key_id.

[adityasaky]

Hi @ashutoshsao, thanks for picking #1 up.

I'd like to modify the scope of #1 a bit. Since the issue was opened, we have actually added several keys https://github.com/in-toto/in-toto-rs/tree/master/tests which are used in tests. I'd like us to focus on interoperability testing. Specifically, let's add an ed25519 key pair here generated using in-toto-keygen and add a test that loads it. I don't see a key in https://github.com/in-toto/in-toto-rs/tree/master/tests/ed25519 that matches the custom securesystemslib format employed by the reference implementation. We don't use a custom format for RSA keys and already have examples in https://github.com/in-toto/in-toto-rs/tree/master/tests/rsa.

Related: #22

[ashutoshsao]

ok @adityasaky on it now !

[ashutoshsao]

hey @adityasaky i have created a new fork and pr