Added CheckPalindrome (#213)

* Added CheckPalindrome contributed by @Swapnil-2001

String/CheckPalindrome.js

@@ -0,0 +1,25 @@
+// Palindrome check is case sensitive; i.e. Aba is not a palindrome
+// input is a string
+const checkPalindrome = (str) => {
+  // check that input is a string
+  if (typeof str !== 'string') {
+    return 'Not a string'
+  }
+  // Store the length of the input string in a variable
+  const length = str.length
+  if (length === 0) {
+    return 'Empty string'
+  }
+  // Iterate through the length of the string
+  // Compare the first character to the last, the second character to the second last, and so on
+  for (let i = 0; i < length / 2; i++) {
+    // at the first instance of a mismatch
+    if (str[i] !== str[length - 1 - i]) {
+      return 'Not a Palindrome'
+    }
+  }
+  return 'Palindrome'
+}
+
+console.log(checkPalindrome('madam'))
+console.log(checkPalindrome('abcd'))