docs: add fast api example (#9418)

# Which Problems Are Solved

The community implemented an example for integrating fastAPI with
Zitadel.
So far this example has not been listed.

# How the Problems Are Solved

The example is now listed
Disclaimer is added, that some of the examples are not maintained by us

docs/frameworks.json

@@ -80,6 +80,12 @@
     "docsLink": "https://github.com/maennchen/zitadel_api",
     "external": true
   },
+  {
+    "title": "FastAPI",
+    "imgSrcDark": "/docs/img/tech/fastapi.svg",
+    "docsLink": "https://github.com/cleanenergyexchange/fastapi-zitadel-auth",
+    "external": true
+  },
   {
     "title": "NextAuth",
     "imgSrcDark": "/docs/img/tech/nextjs.svg",