✨: add CanArrayRSub protocol

Support right subtraction operator for array classes

Author: nstarman

src/array_api_typing/_array.py

@@ -162,6 +162,24 @@ def __isub__(self, other: Self | int | float, /) -> Self:
         ...
 
 
+class CanArrayRSub(Protocol):
+    """Protocol for array classes that support the right subtraction operator."""
+
+    def __rsub__(self, other: Self | int | float, /) -> Self:
+        """Calculates the difference for each element of an array instance with the respective element of the array other.
+
+        The result of self_i - other_i must be the same as self_i + (-other_i) and must be governed by the same floating-point rules as addition (see array.__add__()).
+
+        Args:
+            other: subtrahend array. Must be compatible with self (see Broadcasting). Should have a numeric data type.
+
+        Returns:
+            an array containing the element-wise differences. The returned array must have a data type determined by Type Promotion Rules.
+
+        """  # noqa: E501
+        ...
+
+
 class CanArrayMul(Protocol):
     """Protocol for array classes that support the multiplication operator."""
 
@@ -344,6 +362,7 @@ class Array(
     CanArrayRAdd,
     CanArraySub,
     CanArrayISub,
+    CanArrayRSub,
     CanArrayMul,
     CanArrayIMul,
     CanArrayTrueDiv,