[FEATURE] Setup cargo tests for stego parsing

[jgabaut]

Cargo tests for parsing stego.lock as TOML should be added, along with a stego-examples directory to hold at least two examples, one correct and one wrong.

Reference the files used in amboso stego parsing tests: link

Success is expected for good.stego and lock.stego, failure is expected for bad.stego.

Most likely, the grammar expressed by regex in the bash implementation would not align with our expectations and we may need to adjust our examples, while still keeping the main expected format.

See also #2

[jgabaut]

I doubt this will be done earlier than #39 ... Closing for now.

[jgabaut]

Reopening in view of 0.2.x