[Feature Request]: Add higher orders of multipoles for RDTs

[Maël Le Garrec]

Feature Description

The current RDT implementation is limited to sextupoles and octupoles, as the f-terms are hardcoded at the beginning of rdt.py.

To study higher order RDTs, like $f_{1004}$ generated by decapoles, it is needed to add the f-term lines to the dict.

For those RDT calculations being possible, it is also needed to calculate the amplitude of the lines in harpy. The lines can be found in the RESONANCES dict in frequency.py

Possible Implementation

Either add a bunch of f-terms in rdt.py and the associated amplitude lines in frequency.py
Or write more general functions that would generate those terms/lines given a multipole order.

[Maël Le Garrec]

Fixed by PR #385