Tokio Simple Scheduler

I needed a very basic scheduler with no features, so here it is.

```rust use std::time::Duration;

use chrono::Utc; use tokiosimplescheduler::{Job, Scheduler};

[tokio::main]

async fn main() { let mut scheduler = Scheduler::default(); scheduler.add( Job::new("every 2", "/2 * * * * *", || { Box::pin(async { println!("{:?} - Every 2 seconds", Utc::now()); }) }) .unwrap(), ); scheduler.add( Job::new("every 4", "/4 * * * * ", || { Box::pin(async { println!("{:?} - Every 4 seconds", Utc::now()); }) }) .unwrap(), ); scheduler.add( Job::new("every 5", "/5 * * * * ", || { Box::pin(async { println!("{:?} - Every 5 seconds", Utc::now()); }) }) .unwrap(), ); scheduler.add( Job::new("every 10", "/10 * * * * ", || { Box::pin(async { println!("{:?} - Every 10 seconds", Utc::now()); }) }) .unwrap(), ); scheduler.add( Job::new("every 30", "/30 * * * * *", || { Box::pin(async { println!("this job"); tokio::time::sleep(Duration::fromsecs(3)).await; println!("takes a few"); tokio::time::sleep(Duration::fromsecs(3)).await; println!("seconds to run"); }) }) .unwrap(), ); scheduler.start().await; } ```

It doesn't do anything else.