rotate tool, testCases then updated index file

src/pages/string/rotate/service.ts

@@ -0,0 +1,43 @@
+export function rotate(input: string, step: number, right: boolean): string {
+  const array: string[] = input.split('');
+  const length = array.length;
+
+  if (length === 0) {
+    return input; // Return early if the input is an empty string
+  }
+
+  // Normalize the step to be within the bounds of the array length
+  const normalizedPositions = ((step % length) + length) % length;
+
+  if (right) {
+    // Rotate right
+    return array
+      .slice(-normalizedPositions)
+      .concat(array.slice(0, -normalizedPositions))
+      .join('');
+  } else {
+    // Rotate left
+    return array
+      .slice(normalizedPositions)
+      .concat(array.slice(0, normalizedPositions))
+      .join('');
+  }
+}
+
+export function rotateString(
+  input: string,
+  step: number,
+  right: boolean,
+  multiLine: boolean
+) {
+  const result: string[] = [];
+  if (multiLine) {
+    const array: string[] = input.split('\n');
+    for (const word of array) {
+      result.push(rotate(word, step, right));
+    }
+  } else {
+    result.push(rotate(input, step, right));
+  }
+  return result.join('\n');
+}