Support simd_json (#105)

This PR adds support for the simd-json library whenever decoding or encoding JSON responses. This may be enabled independently of serenity and twilight support for SIMD acceleration.

Co-authored-by: Kyle Simpson <kyleandrew.simpson@gmail.com>

src/input/adapters/cached/compressed.rs

@@ -199,7 +199,7 @@ impl Compressed {
         )?;
         let mut metabytes = b"DCA1\0\0\0\0".to_vec();
         let orig_len = metabytes.len();
-        serde_json::to_writer(&mut metabytes, &metadata)?;
+        crate::json::to_writer(&mut metabytes, &metadata)?;
         let meta_len = (metabytes.len() - orig_len)
             .try_into()
             .map_err(|_| CodecCacheError::MetadataTooLarge)?;

src/input/adapters/cached/error.rs

@@ -1,6 +1,5 @@
-use crate::input::AudioStreamError;
+use crate::{error::JsonError, input::AudioStreamError};
 use audiopus::error::Error as OpusError;
-use serde_json::Error as JsonError;
 use std::{
     error::Error as StdError,
     fmt::{Display, Formatter, Result as FmtResult},