Support representing repeated sequences from varnomen

[holtgrewe]

Is your feature request related to a problem? Please describe.
We can parse and represent the most common small variants pretty well. However, repeated sequence is currently out of scope.

Describe the solution you'd like
Add support parsing and representing of the varnome repeated sequences.

Projecting such variants could be made possible by translating them into sequence representation. This could become another issue, though.

Describe alternatives you've considered
N/A

Additional context
The code for the parser/representation is in the parser module documented here on docs.rs.

Adding support for parsing and representation would be simple enough:

• extend the representation data structure
• extend the nom-based parser for parsing
• add the necessary display code
• add appropriate tests for all