Json Sync

### Describe your improvement idea or feature request

Hey guys! This is awesome! Good to see a nice mobile app under development for TW.

I like to rely on SyncThing for a lot of my file syncing, which works great for text files. The task server works well but it's a dependency I shouldn't need with TW's [json export](https://taskwarrior.org/docs/3rd-party/) (which is apparently the recommended 3rd party integration mechanism). What would it take to support json as a sync option?

### How would you like to see it implemented?

1. Select sync option "json file"
2. Select file/dir

### Put here any screenshots or videos (optional)

_No response_

### How can we contact you (optional)

_No response_

### Would you like to work on this issue?

None

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- [X] I have starred the repo ⭐ and watched 👀 it on GitHub and followed the contribution guidelines.