[E-nodes < T502] Implement nodes.relationship_types

[imilinovic]

Description

Implement nodes.relationship_types

Pull request type

• Bugfix
• Algorithm/Module
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

######################################

Reviewer checklist (the reviewer checks this part)

Module/Algorithm

• Core algorithm/module implementation
• Query module implementation
• Unit tests
• End-to-end tests
• Code documentation
• README short description
• Documentation on memgraph/docs
• Update GQLALchemy signatures in query builder using query module signature generator

######################################

[antepusic]

How would nodes.relationship_types work if the user gives a relationship like e.g. "<KNOWS>"? I think we should add a test for this case.

Also, the question from #300 applies to this module as well.

[antepusic]

Looks good to go!