fix: process must works with async

index.js

@@ -181,10 +181,13 @@ const mutantJson = (target, process, opts) => {
   const processMutation = (value, path, target) => {
     let ret;
 
-    process((patch) => {
+    const presult = process((patch) => {
       ret = applyPatches(patch, path, target);
     }, value, path, target);
 
+    if (isPromise(presult)) {
+      return presult.then(() => ret);
+    }
     return ret;
   };
 

test.js

@@ -452,6 +452,28 @@ test('should mutate using a promise', async (t) => {
   t.deepEqual(actual, expected);
 });
 
+test('should mutate using async', async (t) => {
+
+  const flattenObjectPromises = {
+    foo: Promise.resolve(1),
+    bar: Promise.resolve(2),
+  };
+
+  const expected = {
+    foo: 100,
+    bar: 200,
+  };
+
+  const actual = await mutateJson(Promise.resolve(flattenObjectPromises), async (mutate, value) => {
+    const op = await Promise.resolve({
+      value: value * 100,
+    });
+    mutate(op);
+  });
+
+  t.deepEqual(actual, expected);
+});
+
 
 test('should force return a promise even when no promise detected', async (t) => {