Add intro to Compton imaging

[ckarwin]

It will be helpful to eventually add a dedicated page with an intro to Compton imaging, e.g. similar to the intro to polarization page. This is not a priority, but I'll open this issue as a way to keep track.

[ckarwin]

@hiyoneda has agreed to do this eventually (not necessarily needed for DC3).

[israelmcmc]

If it helps, there's an intro to RL in the gamma ray toys tutorials: https://github.com/israelmcmc/gammaraytoys/blob/main/docs/tutorials/05-binned_RL_spectrum.ipynb

It's technically not imaging since I performed the deconvolution only on the spectrum, but it's the same algorithm. I thought introducing it in a 1D case could be easier to understand, but maybe not, idk

[ckarwin]

Thanks, @israelmcmc. Indeed, maybe this can worked in to the imaging description (or at least referenced).