Fix/code smells (#1338)

* ♻️ refactor: improving and fixing some code

* Updated Documentation in README.md

* ♻️ refactor: improving isLeapYear

* 🐛 chore: back changes

* 🐛 fix: using reduce instead forEach

* 🐛 fix: using reduce instead forEach

* 🐛 fix: removing duplicated code

* 🐛 chore: removing .js

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Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

String/CheckRearrangePalindrome.js

@@ -12,7 +12,7 @@ export const palindromeRearranging = (str) => {
     return 'Not a string'
   }
   // Check if is a empty string
-  if (str.length === 0) {
+  if (!str) {
     return 'Empty string'
   }