refactor: migrate project from C++ to Rust

- establish basic Rust project layout.
- move all old code into independent directory.

wfassoc_dylib/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "wfassoc_dylib"
+version = "0.1.0"
+authors = ["yyc12345"]
+edition = "2024"
+description = "The dynamic wfassoc library exposed for C/C++ and other languages users."
+license = "SPDX:MIT"
+
+[dependencies]
+thiserror = { workspace = true }
+wfassoc = { path="../wfassoc" }

wfassoc_dylib/src/lib.rs

@@ -0,0 +1,14 @@
+pub fn add(left: u64, right: u64) -> u64 {
+    left + right
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_works() {
+        let result = add(2, 2);
+        assert_eq!(result, 4);
+    }
+}