Add missing features in Feature Comparison

[derneuere]

We added now a lot of new programs and categories, but we still need to fill it with data. Every cell marked with a question mark needs to be filled to give the user a complete picture.

[meichthys]

If i knew about this great comparison i probably would have just contributed here instead of having to re-discover the features of other photo programs.

If you'd like to offload the task of keeping the comparison up to date, feel free to reference https://github.com/meichthys/foss_photo_libraries which I plan to keep up to date. I also plan to add more categories and links to issues for features that have not been implemented yet but are in process on each repository.

[pdcemulator]

Added Synology Photos data with #43