fix isImageURL potentially making it more robust to handle different …

[Tishasoumya-02]

Make the isImageURL more robust. Previously it used to only check for particular image type and at times some images added by the llm was not passing the check, but with the current suggesting implementation, it checks -

1. For data URLs, check MIME type
2. For external URLs , Inspecting HTTP Headers (Content-Type)

[danalvrz]

@Tishasoumya-02 I moved the image url validation to the tool handler to keep the processBlocks method synchronous. Please take a look and test it.

[Tishasoumya-02]

@danalvrz , yes it works nicely!

[Tishasoumya-02]

I noticed sometimes , maybe it's the llm , it adds an image but maybe the url is broken few times, maybe there is a way to check it? I'm not sure, can check it if it's possible