Merge pull request #568 from gsmoon97/docs/fix-typo

docs: Fix typo in tips.rst

Author: joke2k

docs/tips.rst

@@ -290,7 +290,7 @@ The following example demonstrates the above:
 Proxy value
 ===========
 
-Values that being with a ``$`` may be interpolated. Pass ``interpolate=True`` to
+Values that begin with a ``$`` may be interpolated. Pass ``interpolate=True`` to
 ``environ.Env()`` to enable this feature:
 
 .. code-block:: python