add .sha256 checksums to binary distribution tarballs (#3605)

Author: cormacrelf

.github/workflows/main.yml

@@ -486,6 +486,7 @@ jobs:
             tmp/$name/
           chmod +x tmp/$name/wasm*
           tar czvf gh-release/$name.tar.gz -C tmp $name
+          sha256sum gh-release/$name.tar.gz > gh-release/$name.tar.gz.sha256sum
         }
         mk x86_64-unknown-linux-musl dist_linux_x86_64_musl
         mk aarch64-unknown-linux-gnu dist_linux_aarch64_gnu
@@ -517,4 +518,4 @@ jobs:
     - uses: softprops/action-gh-release@v1
       if: startsWith(github.ref, 'refs/tags/')
       with:
-        files: "gh-release/*.tar.gz"
+        files: "gh-release/*.tar.gz*"