Function render 

pub fn render(
    lang: &str,
    code: &str,
    options: RenderOptions,
) -> Result<RenderResult, MermaidError>

Unified entry point — render a diagram by language name.

Dispatches to the correct parser based on lang:

• "d2" → D2 parser
• "mermaid" (or any other value) → Mermaid auto-detect (flowchart, state, sequence, pie)

Example

use graphs_tui::{render, RenderOptions};

let result = render("d2", "A -> B", RenderOptions::default()).unwrap();
println!("{}", result.output);