The tool generates the .json file anew

[Zireael07]

Judging by the diffs here on GIT, the tool generates the entire file anew.

I had to copy out the added items, revert the changes and add the items back.

It is a little annoying considering the contributing rules.

[BrianMacIntosh]

I wasn't aware of the contributing rules. I will add an option to export specific entries to accommodate this. Could you link me to said rules?

[Zireael07]

Rules: https://github.com/CleverRaven/Cataclysm-DDA/blob/master/CONTRIBUTING.md

It's not in the rules per se, but several people told me to fix the PR since the diffs are too big for Git to display.

[BrianMacIntosh]

Resolved by adding "Export" function, still planning to attempt to allow Save to leave unchanged parts of the file untouched.