add Wasmi specific if.wast test case

Author: Robbepop

crates/wast/tests/local/if.wast

@@ -0,0 +1,10 @@
+(module
+    (func (export "if.only-then.diverging")
+        (if
+            (i32.const 0) ;; false
+            (then
+                (br 0)
+            )
+        )
+    )
+)

crates/wast/tests/mod.rs

@@ -202,6 +202,7 @@ macro_rules! expand_tests {
             fn wasmi_wide_arithmetic("../../local/wide-arithmetic");
             fn wasmi_replace_result("../../local/replace-result");
             fn wasmi_local_tee("../../local/local-tee");
+            fn wasmi_if("../../local/if");
 
             // Wasm `simd` tests
             fn wasm_simd_address("simd_address");