Create cargo workspace

Signed-off-by: Marcel Müller <neikos@neikos.email>

crates/plaixt-core/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "plaixt-core"
+version.workspace = true
+edition.workspace = true
+description.workspace = true
+license.workspace = true
+
+[dependencies]

crates/plaixt-core/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);
+    }
+}