docs: add brand logo banner to README (#61)

Author: lesnik512

readme.md

@@ -1,4 +1,10 @@
-# fastapi-sqlalchemy-template
+<p align="center">
+  <picture>
+    <source media="(prefers-color-scheme: dark)"  srcset="https://raw.githubusercontent.com/modern-python/.github/main/brand/projects/fastapi-sqlalchemy-template/lockup-dark.svg">
+    <source media="(prefers-color-scheme: light)" srcset="https://raw.githubusercontent.com/modern-python/.github/main/brand/projects/fastapi-sqlalchemy-template/lockup-light.svg">
+    <img alt="fastapi-sqlalchemy-template" src="https://raw.githubusercontent.com/modern-python/.github/main/brand/projects/fastapi-sqlalchemy-template/lockup.png" width="420">
+  </picture>
+</p>
 
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