message: Add write_image_with_speed_quality function.
  Adds an additional method to avif to allow writing an image while specifying the quality and speed.
diff: /// [AVIF]: https://aomediacodec.github.io/av1-avif/
  use std::borrow::Cow;
  use std::io::Write;
  +use std::cmp::{min, max};
  use crate::{ColorType, ImageBuffer, ImageFormat, Pixel};
  use crate::{ImageError, ImageResult};
  @@ -37,7 +38,20 @@ impl<W: Write> AvifEncoder<W> {
  /// necessary. When data is suitably aligned, i.e. u16 channels to two bytes, then the
  /// conversion may be more efficient.
  pub fn write_image(mut self, data: &[u8], width: u32, height: u32, color: ColorType) -> ImageResult<()> {
  - let config = self.config(color);
  + self.write_image_with_speed_quality(data, width, height, color, 100, 1)
  + }
  +
  + /// Encode image data with the indicated color type, quality and speed.
  + ///
  + /// The encoder currently requires all data to be RGBA8, it will be converted internally if
  + /// necessary. When data is suitably aligned, i.e. u16 channels to two bytes, then the
  + /// conversion may be more efficient.
  + pub fn write_image_with_speed_quality(mut self, data: &[u8], width: u32, height: u32, color: ColorType, quality: u8, speed: u8) -> ImageResult<()> {
  + // Clamp quality and speed to range
  + let quality = max(1, min(quality, 100));
  + let speed = max(1, min(speed, 10));
  +
  + let config = self.config(color, quality, speed);
  // `ravif` needs strongly typed data so let's convert. We can either use a temporarily
  // owned version in our own buffer or zero-copy if possible by using the input buffer.
  // This requires going through `rgb`.
  @@ -50,11 +64,11 @@ impl<W: Write> AvifEncoder<W> {
  Ok(())
  }
  - fn config(&self, _color: ColorType) -> Config {
  + fn config(&self, _color: ColorType, quality: u8, speed: u8) -> Config {
  Config {
  - quality: 100,
  - alpha_quality: 100,
  - speed: 1,
  + quality: quality,
  + alpha_quality: quality,
  + speed: speed,
  premultiplied_alpha: false,
  color_space: ColorSpace::RGB,
  }
  