Add example for axum

[vbrandl]

I added an example on how to use ructe with the axum framework.
The example should behave exactly the same as the actix example

[kaj]

Thanks! This looks good. One very minor nitpick (it says warp rather than axum in the example text).

[kaj]

Sorry for the delay. Now I've found the time to look closer at the code. Looks good, I'll merge it soonish.

[kaj]

Cool macro! Simple enough, rather different from what the other examples do, but I like it!

[vbrandl]

It's actually the same macro as used in the actix example. I didn't investigate further but it seemed the actix example did duplicate one branch in the macro. Here is the macro from actix:

macro_rules! render {
    ($template:path) => (Render(|o| $template(o)));
    ($template:path, $($arg:expr),*) => {{
        use actix_ructe::Render;
        Render(|o| $template(o, $($arg),*))
    }};
    ($template:path, $($arg:expr),* ,) => {{
        use actix_ructe::Render;
        Render(|o| $template(o, $($arg),*))
    }};
}

I'm not too deep into Rust macros so I don't know what the trailing , in tha last branch of the macro changes in comparison to the second branch but it works.

[kaj]

Ah, I'd forgotten all about that macro. Ah well. 😎

The trailing comma is to match invocations where this is a trailing comma after the last argument, as is common if the argument list is long enogh to be split on more than one line, like

    render!(
        the_template,
        one_argument,
        another_argument, // <-- here
    )

[vbrandl]

Ah, I see. I think I found a less redundant way by making the trailing comma optional. See cf68d54