Add Apache Arrow sprint (#1416)

Apache Arrow sprint proposal.

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ege Akman <[email protected]>

Author: 3 people

src/content/sprints/apache_arrow.md

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+---
+title: "Apache Arrow"
+numberOfPeople: "TBA"
+pythonLevel: "Intermediate"
+contactPerson:
+  name: "Rok Mihevc"
+  email: "[email protected]"
+links:
+  - title: "Apache Arrow"
+    url: "https://github.com/apache/arrow"
+  - title: "Proposed donation of pyarrow-stubs"
+    url: "https://github.com/apache/arrow/discussions/45919"
+---
+
+We want to add type annotations to the PyArrow project. We will sprint to
+identify best approach to do so by prototyping. Suggestions and discussion also
+welcome.