blog: doc usage of anyhow!

[JosiahParry]

Since extendr/extendr#973 returning anyhow::Result<> works without any modification.

I think this is a huge quality of life improvement. We can make a patch release with these features and document it?

For example:

use anyhow::bail;
use extendr_api::prelude::*;

#[extendr]
fn can_we_anyhow() -> anyhow::Result<()> {
    bail!("This is an error");
    Ok(())
}

lets us return a nice error

[yutannihilation]

Oh, cool. Congratulations!