refactor: refactor ffi design document

assets/c-friendly-ffi-design/rust-side/example.md

@@ -0,0 +1,15 @@
+# FFI Example
+
+
+
+## Rust Core Crate
+
+```rust
+
+```
+
+## Rust FFI Binding Crate
+
+```rust
+
+```