For carbon, peak picking on dept 90 135 / carbon

We could think about the possibility based on different experiment to extract and assign the different signals. This is a pretty specific tool that could allow based on the selection of 2 spectra containing dept90 / dept135 to automatically add an assignment C, CH, CH2, CH3 in the list of peaks or ranges. I still do not have a clear idea how this could be implemented and at which level.

The issue names no files, tests, or entry points. Start by locating the peak-picking and peak-or-range assignment flows, then determine where two selected DEPT90/DEPT135 spectra can be combined. Done should be an agreed implementation that assigns C, CH, CH2, and CH3 labels automatically, with tests covering the selected spectra and resulting peak or range list.

Written by the indexing model from the issue text.