Code block styling feels dated, replace harsh orange Pygments highlighting with a muted, Carbon.sh/Medium-style theme

The current docs use a Pygments highlighting style where prompts (>>>) and keywords (import, function calls) are rendered in a saturated orange (see attached screenshot). Against the light gray code block background, this reads as visually loud and dated compared to modern documentation sites.

Proposed change:

Adopt a more restrained, modern look inspired by carbon.sh and Medium's code blocks:

Muted, low-saturation syntax colors (soft blue/teal/gray) instead of high-saturation orange Reduce the >>> prompt to a neutral gray/muted tone rather than a highlighted color and it's chrome, not content and doesn't need to compete visually with the code Slightly increase code block background contrast/softness (subtle rounded corners, soft shadow, or a slightly darker/lighter tint than body background) for a "card" feel like carbon.sh screenshots Keep enough contrast between keyword/string/comment tokens for readability, but avoid pure saturated hues

Where this likely needs to change: Since the docs use the nltk_theme Sphinx theme (a fork of Insegel), this is probably a Pygments style override either a custom .css in the theme (targeting .highlight .k, .highlight .go for prompts, etc.) or swapping the configured Pygments style in conf.py/theme config for one with a softer palette (e.g. adapting one-dark, github-dark, or a fully custom style).

Why it matters: Cleaner code-block styling improves readability and brings the docs closer to the visual quality of the rest of the modernized site (ref: the 2021 site modernization in #2845), without needing a full redesign

just a Pygments/CSS tweak.