This is about adding support for the memory64 Wasm proposal.

The memory64 Wasm proposal is already in Phase 4 since some time and thus full stabilization can be expected to happen soon.

Having memory64 support in wasmi would improve alignment with Wasmtime, and allow to use Wasmi for Wasm binaries that have been compiled to memory64 (obviously). However, it would also allow to use Wasmi for Wasm binaries that require more than 4GB of linear memory to properly execute which might be a niche use-case given that Wasmi is an interpreter but there still might exist some use cases for it.