Add rule for detecting if a dependency is explicitly installed

[fvictorio]

Similar to node/no-extraneous-require.

For example, if a contract does import "@openzeppelin/contracts/token/ERC721/ERC721.sol"; but @openzeppelin/contracts is not installed, an error should be emitted.

I'm not sure if this should be a core rule or a plugin. If there are other possible rules related to dependencies, maybe it would make more sense to make a plugin (but I can't think of some other right now).