(ml5717) Split up CRDT into module structure

Cargo.toml

pkg/drawing_crdt_bg.wasm

src/crdt/deltavec/mod.rs

src/crdt/deltavec/serde.rs

src/crdt/dirty.rs

src/crdt/interval/bound.rs

src/crdt/interval/mod.rs

src/crdt/interval/serde.rs

src/crdt/interval/union/mod.rs

src/crdt/interval/union/serde.rs

src/crdt/interval/union/state/mod.rs

src/crdt/interval/union/state/serde.rs

src/crdt/mod.rs

src/crdt/statevec/mod.rs

src/crdt/statevec/serde.rs

src/crdt/stroke/delta/mod.rs

src/crdt/stroke/delta/serde.rs

src/crdt/stroke/id/mod.rs

src/crdt/stroke/id/serde.rs

src/crdt/stroke/mod.rs