Add new release artifact x86_64-unknown-linux-musl (#834)

Author: andros21

.github/workflows/release.yml

@@ -35,6 +35,9 @@ jobs:
             artifact-name: stylua-linux-x86_64
             artifact-alias: stylua-linux
             cargo-target: x86_64-unknown-linux-gnu
+          - os: ubuntu-20.04
+            artifact-name: stylua-linux-x86_64-musl
+            cargo-target: x86_64-unknown-linux-musl
           - os: ubuntu-20.04
             artifact-name: stylua-linux-aarch64
             cargo-target: aarch64-unknown-linux-gnu