about making breaking changes to serialization format

As I was looking at potentially implementing more features from https://github.com/brave/adblock-rust/issues/1 and https://github.com/brave/adblock-rust/labels/uBO-parity, I noticed that `NetworkFilterMask` is already full, and in order to add more bit flags, it would need to be expanded from `u32` to `u64`. That will create a breaking change to the on-disk serialization format. What is the current policy about this?

Start by reading the NetworkFilterMask discussion in this issue and the linked feature and uBO parity issues. Determine the project's current policy for breaking changes to the on-disk serialization format and whether expanding the mask is acceptable. Done means the policy and any constraints are documented or a clear decision is recorded.

Written by the indexing model from the issue text.