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Added README for Annif-VLM-demo with deployment instructions and environment variables.

.github/README.md

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+# Annif-VML-demo
+
+Developed using Copilot Agent.
+
+Deploy as a Hugging Face Space by just pushing the code to the HF; you can e.g. add HF as a new remote:
+
+    git remote add huggingface git@hf.co:spaces/NatLibFi/Annif-VLM-demo
+
+The app needs these environment variables:
+- `ANNIF_API_BASE_URL`
+- `VLM_API_KEY`
+- `VLM_API_BASE_URL`
+
+When developing you can use autoreload by running the app like this:
+
+    gradio app.py
+