Metaspace-converter

Adds support to download and convert datasets processed chemical modifications or neutral loss.

* Colocalization analysis was added to the package
* This is a common metric for the analysis of imaging MS/spatial metabolomics data.
* In a previous publication ([ColocML](https://academic.oup.com/bioinformatics/article/36/10/3215/5734647)), processing steps for colocalization were evaluated and the best performing processing was implemented for this package.
* The `anndata_to_image_array` function can now extract images from layers of the `AnnData` object

Updates in the documentation

First release of metaspace-converter python package.