docs: Update docs for Python in Fable v5

[dbrattli]

Update Python documentation

Added documentation for new Python features in Fable v5.0.0:

• Py.python - inline Python code embedding
• Py.Decorator - Python decorator support for classes and functions
• Py.ClassAttributes - control class member generation
• Record field casing behavior (v5.0.0-alpha.14)
• importSideEffects function
• Python version requirements (3.12+, 3.14 supported)
• PyPI publishing with --fableLib option

Features include code examples and version tags.

[dbrattli]

@MangelMaxime is this the right way to tag at this point, or should I add -alpha to the tags?

<p class="tag is-info is-medium">
    Added in v5.0.0
</p>

[MangelMaxime]

@MangelMaxime is this the right way to tag at this point, or should I add -alpha to the tags?

<p class="tag is-info is-medium">
    Added in v5.0.0
</p>

I think we should use the real version if possible to avoid confusion.

Perhaps, once we released Fable 5 we will just mark everything as Added in v5.0.0 if it makes more sense.

[MangelMaxime]

Small rewording proposition what do you think?

[dbrattli]

@MangelMaxime Thanks for the feedback and suggestions. Agree on the version tags. I will update them later today (or tomorrow).