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>

.github/workflows/ci.yml

@@ -39,6 +39,7 @@ jobs:
           - Windows
           - driver only
           - gateway only
+          - simd json
 
         include:
           - name: beta
@@ -55,6 +56,10 @@ jobs:
           - name: gateway only
             features: serenity-rustls
             dont-test: true
+          - name: simd json
+            features: simd-json serenity-rustls driver gateway serenity/simd_json
+            rustflags: -C target-cpu=native
+            dont-test: true
 
     steps:
       - name: Checkout sources
@@ -94,6 +99,10 @@ jobs:
             target
           key: ${{ runner.os }}-test-${{ steps.tc.outputs.rustc_hash }}-${{ hashFiles('**/Cargo.toml') }}
 
+      - name: Set RUSTFLAGS
+        if: runner.os != 'Windows'
+        run: echo "RUSTFLAGS=${{ matrix.rustflags || '' }}" >> $GITHUB_ENV
+
       - name: Build all features
         if: matrix.features == ''
         run: cargo build --features full-doc