Add Mod Loader and MC Version changes to diff

[Wxrlds]

• Adds sections # Minecraft and # Loaders to the diff output
• Add header-size option to specify number of # in front of the headings
• Add test to make sure diff has correct format

[juraj-hrivnak]

Thank you for the PR. I see very good things like: instead of using mutable collections, you are using map(); also the printing and writing to file side effects are separate from the main function.

The resources for the tests should not be included like this. The best would be to generate them when the tests are set up and then clean them up afterwards. Also instead of using a Python script like this, it should be generated in the setup.

Feel free to ask if anything is not clear and good luck!

[juraj-hrivnak]

This function could be generalized to work for each type of change, if possible. Some patterns repeat, you could probably do it similarly to the above example.

[Wxrlds]

I see your point, but the biggest problem I see here is that every time we write to a file, we check if there are more changes in the loaders or projects to insert the newline.

And since the different change types (MC version, loader, project) are looking for the next loader and project or just loader or just project, I don't see an easy way to do this.