77: add statement on Central compatibility

[lindsay-stevens]

Closes #77

What has been done to verify that this works as intended?

Tested pyODK with v2024.1.0 as deployed on https://staging.getodk.cloud/

Why is this the best possible solution? Were any other approaches considered?

See #77

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

Advises users on expected compatibility with Central.

Do we need any specific form for testing your changes? If so, please attach one.

N/A

Does this change require updates to documentation? If so, please file an issue here and include the link below.

N/A

Before submitting this PR, please make sure you have:

• included test cases for core behavior and edge cases in tests
• run python -m unittest and verified all tests pass
• run ruff format pyodk tests and ruff check pyodk tests to lint code
• verified that any code or assets from external sources are properly credited in comments

[yanokwa]

We should add updating this text to the release section of the read me.