Interpolating data for higher-resolution pathway studies

Issue first opened as a PR in PyPSA-Eur's PR #1986, now rightfully closed. For congruence, I'll copy-paste here the PR as was, with the caveat that the proposed were a work-around for PyPSA-Eur, not technology-data.

I've been toying around with the possibility of running year-by-year miopic optimisation. Shortly, I found that the only two extant obstacles were:

• Missing yearly biomass potentials
• Missing yearly technology costs

Thus, I've changed two things in this PR. First, I've created an elementary script that linearly interpolates the biomass potentials. Secondly, I've changed the retrieve.smk rule for the costs data from technology-data's `output'.

I'd like to ask if it possible to either:

• Generate a year-by-year technology data for myoptic optimisation in PyPSA-Eur that would like to investigate finer pathways resolutions, or
• Generate a script that locally interpolates data, thus retaining the existent structure in technology-data and interpolate the data locally for each user.

Start by reviewing the referenced PyPSA-Eur retrieve.smk rule and the technology-data outputs, then compare the two proposed approaches for year-by-year values. Done would be a documented, working way to provide interpolated biomass potentials and technology costs for finer-resolution pathway studies without breaking the existing data structure.