add textencoder test case

uni_modules/uts-tests/utssdk/TextEncoder.uts

@@ -9,6 +9,19 @@ export function testEncoder() : Result {
       console.log(int8); // Uint8Array(3) [226, 130, 172]
       // #END
       expect(int8.toString()).toEqual("226,130,172");
+      
+      let ret1:Array<any> = []
+      let ret2:Array<any> = []
+      for(let item of int8){
+      	ret1.push(item)
+      }
+      for(let item of int8){
+      	ret2.push(item)
+      }
+      expect(ret1.toString()).toEqual("-30,-126,-84");
+      expect(ret2.toString()).toEqual("-30,-126,-84");
+      
+      
     })
   })
 }
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