Continue support for taskwarrior 2.x as well as 3.x

### Describe your improvement idea or feature request

Taskwarrior development towards 3.x is great, but many of us are still going to be using task 2.x because of database changes, regressions, etc., so I am hoping that taskwarrior-flutter development and testing does not leave the 2.x branch behind. Thanks

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

continued testing on the 2.x AND 3.x branches

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

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### How can we contact you (optional)

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

None

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