Implement From for anyhow errors

I would like to use question mark operator to propagate anyhow::Result inside functions which returns eyre::Result

fn main() -> eyre::Result<()> {
    example()?;
    Ok(())
}

fn example() -> anyhow::Result<()> {
    anyhow::bail!("anyhow error!")
}

error.log

```rust the trait bound `anyhow::Error: std::error::Error` is not satisfied the following other types implement trait `FromResidual`: as FromResidual>> as FromResidual>> required for `ErrReport` to implement `From` required for `Result<(), ErrReport>` to implement `FromResidual>` ```

eyre-rs / eyre

Implement From for anyhow errors #171