feat: add eval test cases for empty graph and isImpliedBy

[jeswr]

Test cases addressing:

• https://github.com/w3c/N3/issues/185
• https://github.com/w3c/N3/issues/157

There may be a problem with some of these test cases as some:

• Contain literals in the subject position

• Contain variables

  Neither of which is actually permitted in the n-quads spec. A solution for those test cases could be to have the same content for the result but contained in another n3 document. What do you think @william-vw ?

[william-vw]

@jeswr

A solution for those test cases could be to have the same content for the result but contained in another n3 document.

Just to be sure, you mean keeping the results in an n3 results file instead of n-triples / n-quads?

[jeswr]

Just to be sure, you mean keeping the results in an n3 results file instead of n-triples / n-quads?

Correct

[william-vw]

@jeswr yes I think that makes a lot of sense!

[jeswr]

I've updated the files @william-vw .

I'll also respond to https://github.com/w3c/N3/pull/202#discussion_r1282267906 in due course when I have time to write a full response.