feat: add ShapeError

Author: siliconlad

src/error.rs

@@ -0,0 +1,20 @@
+use std::fmt;
+
+#[derive(Debug, Clone)]
+pub struct ShapeError {
+    reason: String,
+}
+
+impl ShapeError {
+    pub fn new(reason: &str) -> Self {
+        ShapeError {
+            reason: reason.to_string(),
+        }
+    }
+}
+
+impl fmt::Display for ShapeError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "ShapeError: {}", self.reason)
+    }
+}