Add [Online Notepad]

[codinghardnowon]

Add https://onlinenotep.ad to Notepads and Notebooks

It is a fast, distraction-free online notepad that saves text automatically in the browser without requiring an account. It focuses on simplicity, mobile responsiveness, and supports multiple languages. It does not cloud storage and collaboration features.

Added at the end of the notepad section as per the contribution guidelines. Let me know if any changes are needed.

By submitting this pull request I confirm I've read and complied with the below requirements.

Failure to properly do so will just result in the pull request being closed and everyone's time wasted. Please read it twice. Most people miss many things.

• [x] I have read the Contribution guidelines and I am confident that my PR is suitable.
• [x] This pull request has a descriptive title. For example, Add [App name], not Update readme.md or Added new entries.
• [x] The app I added is not a duplicate.