enable caching

[bertsky]

I wonder if browsing can be speeded up by enabling @st.cache for inspector.visualize_image. I have tried with various options (allow_output_mutation=True, persist=True, even various hash_funcs= trying to avoid hashing certain types). But whatever I do, the server becomes extremely slow as soon as caching is activated.

[bertsky]

Along the same lines, adding multithreading to the Streamlit server could be worthwhile to improve performance. This seems to be quite an undertaking at the moment though, cf. comments here and here.