Add migrator for Python 3.13

.ci_support/migrations/python313.yaml

@@ -0,0 +1,42 @@
+migrator_ts: 1724712607
+__migrator:
+    commit_message: Rebuild for python 3.13
+    migration_number: 1
+    operation: key_add
+    primary_key: python
+    ordering:
+        python:
+            - 3.6.* *_cpython
+            - 3.7.* *_cpython
+            - 3.8.* *_cpython
+            - 3.9.* *_cpython
+            - 3.10.* *_cpython
+            - 3.11.* *_cpython
+            - 3.12.* *_cpython
+            - 3.13.* *_cp313  # new entry
+            - 3.6.* *_73_pypy
+            - 3.7.* *_73_pypy
+            - 3.8.* *_73_pypy
+            - 3.9.* *_73_pypy
+    paused: false
+    longterm: true
+    pr_limit: 20
+    max_solver_attempts: 3  # this will make the bot retry "not solvable" stuff 12 times
+    exclude:
+        # this shouldn't attempt to modify the python feedstocks
+        - python
+        - pypy3.6
+        - pypy-meta
+        - cross-python
+        - python_abi
+        # see https://github.com/conda-forge/scipy-feedstock/pull/283
+        - scipy
+    exclude_pinned_pkgs: false
+
+python:
+- 3.13.* *_cp313
+# additional entries to add for zip_keys
+numpy:
+- 2
+python_impl:
+- cpython