Support increment/decrement operations in Workers KV

Currently, Workers KV only supports read/write and list operations.

I’m considering my options with regards to building an API, and an increment/decrement operation in this feature would be nice for rate limiting API keys to a certain number of requests per day (or another time frame).

Workers KV is currently a distributed, last-write-wins store. For the aforementioned use case, it means if a key containing the daily usage value hasn’t been propagated to a given edge location, the worker may read the older value and write it, and thereby causing the correct value (which hasn’t been propagated yet) to be discarded for the older value.

Increment/decrement operations would allow for discrepancies to be reconciled between various edge locations as they are very specific manipulations where the order does not matter.