fix: update attention matrix label color scale value from -1.0 to 0.0

[Gabriellavoura]

Fix: Correct softmax range in attention matrix visualization

Hi there! First of all, thanks for this awesome project.
As reported in issue #31, there’s a small mistake in the attention matrix softmax range.

This PR fixes the label of the attention matrix and updates the article image to reflect the corrected range.

Changes

• Adjusts the lower bound of the color scale in AttentionMatrix.svelte from -1.0 to 0.0, ensuring it reflects the valid range of softmax scores ($0 < softmax() <1$).
• Updates the article image to match the corrected visualization.

PS

I accidentally closed the previous PR when I deleted the fork from my GitHub. 😅