dir-embed 0.3.0

Simple way to use [`include_bytes!`](https://doc.rust-lang.org/std/macro.include_bytes.html) for directories.

# Why

I wanted to include a directory for my microcontroller project, but none of the solutions I used before seems to work in a no_std environment.

# Example 

You can embed files three ways.

## Bytes mode

```rust
use dir_embed::Embed;

#[derive(Embed)]
#[dir = "../web/static"] // Path is relativ to the current file
#[mode = "bytes"] // Is the default. Can be omitted.
pub struct Assets;

fn main(){
    let file: &[u8] = Assets::get("css/style.css").expect("Can't find file");

    let string = str::from_utf8(file).expect("Failed to parse file");

    println!("{string}");
}
```

## Str mode

```rust
use dir_embed::Embed;

#[derive(Embed)]
#[dir = "../web/static"] // Path is relativ to the current file
#[mode = "str"]
pub struct Assets;

fn main(){
    let file: &str = Assets::get("css/style.css").expect("Can't find file");

    println!("{file}");
}
```

## Mime mode
Same as "Bytes mode" but also add the guessed mime type from [`mime_guess`](https://crates.io/crates/mime_guess). 
Defaults to `application/octet-stream` for unknown types.

```rust
use dir_embed::Embed;

#[derive(Embed)]
#[dir = "../web/static"] // Path is relativ to the current file
#[mode = "mime"] 
pub struct Assets;

fn main(){
    let file: (&[u8],&str) = Assets::get("css/style.css").expect("Can't find file");

    let string = str::from_utf8(file.0).expect("Failed to parse file");

    println!("{string}");
    println!("MIME: {file.1}"); // text/css
}
```