added support for nested lists

[franz-sw]

Add Full Support for Nested Lists in RichText Editor

This pull request introduces comprehensive support for nested lists, including both OrderedList and UnorderedLists.

Key Features:

• RichTextState Support: Added core functionality to handle nested lists.
• Markdown Support: Correct parsing and rendering for nested lists in Markdown.
• HTML Support: Proper rendering for nested lists in HTML phrasing.

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Nested List Behavior:

Nesting levels are managed using an enum (ListNestedLevel) that supports three levels:

1. Default indentation
2. One level deeper
3. Two levels deeper

Example:

You can control nesting levels programmatically with these public functions:

• RichTextState.increaseListNestedLevel()
• RichTextState.decreaseListNestedLevel()

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Testing

To keep this PR focused, sample updates were excluded. You can test the functionality by adding the following snippet to RichTextStyleRow:

item {
    RichTextStyleButton(
        onClick = {
            state.decreaseListNestedLevel()
        },
        icon = Icons.AutoMirrored.Outlined.FormatIndentDecrease,
    )
}

item {
    RichTextStyleButton(
        onClick = {
            state.increaseListNestedLevel()
        },
        icon = Icons.AutoMirrored.Outlined.FormatIndentIncrease,
    )
}

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This implementation provides a streamlined approach to nested list management, enhancing both Markdown and HTML capabilities. Feedback and suggestions are welcome! 🎉