🛠️ Add CITATION.cff file for academic citations (#13)

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

CITATION.cff

@@ -0,0 +1,24 @@
+# This CITATION.cff file was generated with cffinit.
+# Visit https://bit.ly/cffinit to generate yours today!
+
+cff-version: 1.2.0
+title: SQLModel
+message: >-
+  If you use this software, please cite it using the
+  metadata from this file.
+type: software
+authors:
+  - given-names: Sebastián
+    family-names: Ramírez
+    email: tiangolo@gmail.com
+identifiers:
+repository-code: 'https://github.com/tiangolo/sqlmodel'
+url: 'https://sqlmodel.tiangolo.com'
+abstract: >-
+  SQLModel, SQL databases in Python, designed for
+  simplicity, compatibility, and robustness.
+keywords:
+  - fastapi
+  - pydantic
+  - sqlalchemy
+license: MIT