Python: Add change note for tarslip query.

Author: markshannon

change-notes/1.22/analysis-python.md

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+# Improvements to Python analysis
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+
+## General improvements
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+
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+### Impact on existing queries.
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+
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+## New queries
+
+| **Query** | **Tags** | **Purpose** |
+|-----------|----------|-------------|
+| Arbitrary file write during tarfile extraction (`py/tarslip`) | security, external/cwe/cwe-022 | Finds instances where extracting from a tar archive can result in arbitrary file writes. Results are not shown on LGTM by default. |
+