create palindrome tool, testCases and undated index file

src/pages/string/create-palindrome/service.ts

@@ -0,0 +1,35 @@
+import { reverseString } from 'utils/string'
+
+export function createPalindrome(
+    input: string,
+    lastChar: boolean  // only checkbox is need here to handle it [instead of two combo boxes]
+) {
+    if (!input) return '';
+    let result: string;
+    let reversedString: string;
+
+    // reverse the whole input if lastChar enabled
+    reversedString = lastChar ? reverseString(input) : reverseString(input.slice(0, -1));
+    result = input.concat(reversedString);
+    return result;
+}
+
+export function createPalindromeList(
+    input: string,
+    lastChar: boolean,
+    multiLine: boolean
+): string {
+    if (!input) return '';
+    let array: string[];
+    let result: string[] = [];
+
+    if (!multiLine) return createPalindrome(input, lastChar);
+    else {
+        array = input.split('\n');
+        for (const word of array) {
+            result.push(createPalindrome(word, lastChar));
+        }
+    }
+    return result.join('\n');
+    
+}