feat(Resolver): make addFilterArg asynchronous

```js
someResolver.addFilterArg({
    name: 'isActive',
    type: 'Boolean!',
    description: 'Active status filter',
    query: async (query, value, resolveParams) => {
        const checkPermissions = await Promise.resolve('accessGranted');
        if (checkPermissions) {
          query.isActive = value;
        }
    },
});
```

Closes #31

src/Resolver.js

@@ -448,13 +448,13 @@ export class Resolver<TSource, TContext> {
     const resolveNext = resolver.getResolve();
     const query = opts.query;
     if (query && isFunction(query)) {
-      resolver.setResolve(resolveParams => {
+      resolver.setResolve(async resolveParams => {
         const value = objectPath.get(resolveParams, ['args', 'filter', opts.name]);
         if (value !== null && value !== undefined) {
           if (!resolveParams.rawQuery) {
             resolveParams.rawQuery = {}; // eslint-disable-line
           }
-          query(resolveParams.rawQuery, value, resolveParams);
+          await query(resolveParams.rawQuery, value, resolveParams);
         }
         return resolveNext(resolveParams);
       });

src/__tests__/Resolver-test.js

@@ -548,7 +548,7 @@ describe('Resolver', () => {
       expect(ageType.ofType).toBe(GraphQLInt);
     });
 
-    it('should prepare resolveParams.rawQuery when `resolve` called', () => {
+    it('should prepare resolveParams.rawQuery when `resolve` called', async () => {
       let rpSnap;
       const resolve = resolver.resolve;
       resolver.resolve = rp => {
@@ -571,13 +571,14 @@ describe('Resolver', () => {
           name: 'isActive',
           type: 'Boolean!',
           description: 'Active status filter',
-          query: (query, value, resolveParams) => {
+          query: async (query, value, resolveParams) => {
+            query.checkPermissions = await Promise.resolve('accessGranted'); // eslint-disable-line no-param-reassign
             query.isActive = value; // eslint-disable-line no-param-reassign
           },
           filterTypeNameFallback: 'FilterOtherUniqueNameInput',
         });
 
-      newResolver.resolve({
+      await newResolver.resolve({
         args: { filter: { age: 15, isActive: false } },
         someKey: 16,
       });
@@ -586,6 +587,7 @@ describe('Resolver', () => {
         age: { $gt: 15 },
         isActive: false,
         someKey: 16,
+        checkPermissions: 'accessGranted',
       });
     });