Python: Update change note for 1.22.

Author: taus-semmle

change-notes/1.22/analysis-python.md

@@ -6,9 +6,26 @@
 ### Points-to
 Tracking of "unknown" values from modules that are absent from the database has been improved. Particularly when an "unknown" value is used as a decorator, the decorated function is tracked.
 
+### Loop unrolling
+The extractor now unrolls a single iteration of loops that are known to run at least once. This improves analysis in cases like the following
 
-### Impact on existing queries.
+```python
+if seq:
+    for x in seq:
+        y = x
+    y  # y is defined here
+```
 
+### Better API for function parameter annotations
+Instances of the `Parameter` and `ParameterDefinition` class now have a `getAnnotation` method that returns the corresponding parameter annotation, if one exists.
+
+### Improvements to the Value API
+The Value API has been extended with classes representing functions, classes, tuples, and other types.
+
+### Other improvements
+
+- Short flags for regexes (e.g. `re.M` for multiline regexes) are now handled correctly.
+- Modules with multiple import roots no longer get multiple names.
 
 ## New queries