Attribute Macro async_backtrace::framed

#[framed]

Include the annotated async function in backtraces and taskdumps.

This, for instance:

#[async_backtrace::framed]
async fn foo() {
    bar().await;
    baz().await;
}

…expands, roughly, to:

async fn foo() {
    async_backtrace::frame!(async move {
        bar().await;
        baz().await;
    }).await;
}