document limit & offset query parameters for submissions REST API, fixes getodk/central#1099

[brontolosone]

Fixes getodk/central#1099

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

CI

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

N/A

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?

N/A

Does this change require updates to the API documentation? If so, please update docs/api.yaml as part of this PR.

it IS an update to the API documentation 🤣

Before submitting this PR, please make sure you have:

• run make test and confirmed all checks still pass OR confirm CircleCI build passes
• verified that any code from external sources are properly credited in comments or that everything is internally sourced

[matthew-white]

Suggested change

	description: The maximum number of entries to return.
	description: The maximum number of submissions to return.

No strong feelings, might just be a little clearer this way.

[matthew-white]

Suggested change

	description: The zero-indexed number of entries to skip from the result.
	description: The number of submissions to skip from the result (starting with the latest submission).

I could see the term "zero-indexed" being slightly confusing in this context. If you specify offset=0, that means "skip 0 entries", not "skip 1 entry". It feels more like a count than an index, like 0 doesn't refer to "the first one".

Or is "zero-indexed" there to clarify that "we're skipping from the start (from the zero-indexed submission, i.e., the latest submission)"?

I've suggested some alternative text (which may be unclear in its own way 😅) — let me know what you think.