GH-116738: document thread-safety of bisect

Author: nascheme

Doc/library/bisect.rst

@@ -24,6 +24,16 @@ method to determine whether a value has been found.  Instead, the
 functions only call the :meth:`~object.__lt__` method and will return an insertion
 point between values in an array.
 
+    .. note::
+
+      The functions in this module are not thread-safe. If multiple threads
+      concurrently use :mod:`bisect` functions on the same sequence, this
+      may result in undefined behaviour. Likewise, if the provided sequence
+      is mutated by a different thread while a :mod:`bisect` function
+      is operating on it, the result is undefined. For example, using
+      :py:func:`~bisect.insort_left` on the same list from multiple threads
+      may result in the list becoming unsorted.
+
 .. _bisect functions:
 
 The following functions are provided: