Add mem{8,16,32} to machine.

typeshed/stdlib/machine.pyi

@@ -68,3 +68,25 @@ def time_pulse_us(
     :return: The duration of the pulse in microseconds, or -1 for a timeout waiting for the level to match ``pulse_level``, or -2 on timeout waiting for the pulse to end
     """
     ...
+
+
+class mem:
+    """The class for the ``mem8``, ``mem16`` and ``mem32`` memory views."""
+    def __getitem__(self, address: int) -> int:
+        """Access a value from memory."""
+        ...
+    def __setitem__(self, address: int, value: int) -> None:
+        """Set a value at the given address."""
+        ...
+
+
+mem8: mem
+"""8-bit (byte) view of memory."""
+
+
+mem16: mem
+"""16-bit view of memory."""
+
+
+mem32: mem
+"""32-bit view of memory."""