urandom: add stubs and docs for urandom module

Issue: https://github.com/pybricks/support/issues/236

src/urandom/__init__.py

@@ -0,0 +1,117 @@
+# SPDX-License-Identifier: MIT
+# SPDX-License-Identifier: PSF-2.0
+# Copyright (c) 2021 The Pybricks Authors
+#
+# Portions of the documentation copied from:
+# https://docs.python.org/3/library/random.html
+# Copyright (c) 2001-2021 Python Software Foundation
+
+"""
+This module implements pseudo-random number generators.
+
+.. note:: This module is not available on the BOOST Move Hub.
+
+    You can make your own random number generator like this instead::
+
+        _rand = hub.battery.voltage() + hub.battery.current()  # seed
+
+        # Return a random integer N such that a <= N <= b.
+        def randint(a, b):
+            global _rand
+            _rand = 75 * _rand % 65537  # Lehmer
+            return _rand * (b - a + 1) // 65537 + a
+"""
+
+from typing import Any, Optional, Sequence, overload
+
+
+[
+    "random",
+    "uniform",
+]
+
+# bookkeeping
+
+
+def seed(a: Optional[int] = None) -> None:
+    """
+    Initialize the random number generator.
+
+    Args:
+        a: Optional seed value. If ``None``, the system timer will be used.
+
+    .. tip:: This is called when the module is imported, so normally you do
+        not need to call this.
+    """
+
+
+# integers
+
+
+@overload
+def randrange(stop: int) -> int:
+    ...
+
+
+@overload
+def randrange(start: int, stop: int) -> int:
+    ...
+
+
+@overload
+def randrange(start: int, stop: int, step: int) -> int:
+    ...
+
+
+def randrange(start, stop, step):
+    """
+    Returns a randomly selected element from ``range(start, stop, step)``.
+    """
+
+
+def randint(a: int, b: int) -> int:
+    """
+    Returns a random integer *N* such that ``a`` <= *N* <= ``b``.
+    """
+
+
+def getrandbits(k: int) -> int:
+    """
+    Returns a non-negative integer with ``k`` random bits.
+    """
+
+
+# sequences
+
+
+def choice(seq: Sequence[Any]) -> Any:
+    """
+    Returns a random element from the non-empty sequence ``seq``.
+
+    If ``seq`` is empty, raises ``IndexError``.
+    """
+
+
+# real
+
+
+def random() -> float:
+    """
+    Return the next random floating point number in the range [0.0, 1.0).
+
+    .. tip:: The `interval notation`_ indicates that this includes 0.0 and
+        excludes 1.0.
+
+    .. _interval notation:
+        https://en.wikipedia.org/wiki/Interval_(mathematics)#Notations_for_intervals
+    """
+
+
+def uniform(a: float, b: float) -> float:
+    """
+    Returns a random floating point number *N* such that ``a`` <= *N* <= ``b``
+    for ``a`` <= ``b`` and ``b`` <= *N* <= ``a`` for ``b`` < ``a``.
+
+    The end-point value ``b`` may or may not be included in the range depending
+    on floating-point rounding in the equation ``a + (b-a) * random()``.
+    """