feat: add LaTeX support in ft.Markdown

[7576457]

Description

The flutter_markdown package is officially deprecated and has been replaced by flutter_markdown_plus. In this PR, I updated the old package and also added flutter_markdown_plus_latex.

For the ft.Markdown component, two new attributes are now available:

• latex_style: accepts an ft.TextStyle object.
• latex_scale_factor: accepts a floating-point number.

Test Code

import flet as ft

markdown = """
# Flet Markdown & LaTeX Demo

**Markdown rendering** _with_ selectable text and **LaTeX math formulas**.

- [Flet website](https://docs.flet.dev)
- https://github.com/flet-dev/flet

## Styling

Style text as _italic_, __bold__, ~~strikethrough~~, or `inline code`.

- Use bulleted lists
- To better clarify
- Your points

## Math

Inline formula:
$E = mc^2$

Block formula:
$$
P + \\frac{1}{2} \\rho v^2 + \\rho g h = \\text{constant}
$$

$$
\\int_0^1 x^2 , dx = \\frac{1}{3}
$$

"""


def main(page: ft.Page):
    page.scroll = ft.ScrollMode.AUTO
    page.add(
        ft.Markdown(
            value=markdown,
            selectable=True,
            extension_set=ft.MarkdownExtensionSet.GITHUB_WEB,
            code_theme=ft.MarkdownCodeTheme.ATOM_ONE_DARK,
            latex_style=ft.TextStyle(color="purple"),
            latex_scale_factor=1.2,
        )
    )


ft.run(main)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist

• I signed the CLA.
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• New and existing tests pass locally with my changes
• I have made corresponding changes to the documentation (if applicable)

Screenshots

Summary by Sourcery

Add LaTeX rendering support to the Markdown control and migrate to the new markdown package.

New Features:

• Support rendering LaTeX formulas in the Markdown control, including custom text style and scale factor options.

Enhancements:

• Replace the deprecated flutter_markdown dependency with flutter_markdown_plus and integrate its LaTeX extension package for markdown processing.

[FeodorFitsner]

Individual imports were replaced with import 'package:flet/flet.dart';.
For consistency, use individual imports instead of import "with everything".

[FeodorFitsner]

Great PR! Replacing deprecated package and LaTeX support is a great plus.

[yunguangli]

Awesome, I have been waiting for LaTex support. An can this LaTex mark down can be integrated with Canvas Text too? It would be great for making educational apps.