fix(dropWhile): dropWhile returns the whole array when every element does not match the predicate (#49)

* fix: bug in dropWhile

* test: adds testcase for dropRightWhile

* Update src/array/dropWhile.ts

---------

Co-authored-by: Sojin Park <raon0211@gmail.com>

src/array/dropRightWhile.spec.ts

@@ -21,5 +21,7 @@ describe('dropRightWhile', () => {
         enabled: true,
       },
     ]);
+
+    expect(dropRightWhile([1, 2, 3], x => x < 4)).toEqual([]);
   });
 });

src/array/dropWhile.spec.ts

@@ -18,5 +18,7 @@ describe('dropWhile', () => {
       },
       { id: 3, enabled: false },
     ]);
+
+    expect(dropWhile([1, 2, 3], x => x < 4)).toEqual([]);
   });
 });

src/array/dropWhile.ts

@@ -17,5 +17,9 @@
  */
 export function dropWhile<T>(arr: readonly T[], canContinueDropping: (item: T) => boolean): T[] {
   const dropEndIndex = arr.findIndex(item => !canContinueDropping(item));
+  if (dropEndIndex === -1) {
+    return [];
+  }
+  
   return arr.slice(dropEndIndex);
 }