Chore: builtin right mime of .js (#1808)

constant/mime/mime.go

@@ -0,0 +1,16 @@
+package mime
+
+import (
+	"mime"
+)
+
+var consensusMimes = map[string]string{
+	// rfc4329: text/javascript is obsolete, so we need to overwrite mime's builtin
+	".js": "application/javascript; charset=utf-8",
+}
+
+func init() {
+	for ext, typ := range consensusMimes {
+		mime.AddExtensionType(ext, typ)
+	}
+}