Consider adding following meta information:

 <meta name="description" content="{your description}">
 <meta name="keywords" content="{Your tags here}">
  <meta name="author" content="{Author name}">
<title>Keeper</title>

You could also consider changing the favicon to something like this:

Consider setting a max allowed character for the title. The title text currently overflows the note 'container'

manifest.json data could be updated to provide mobile-users more information about the app.

https://developer.mozilla.org/en-US/docs/Web/Manifest
manifest.json: provides information about an application (such as name, author, icon, and description) in a JSON text file. The purpose of the manifest is to install web applications to the homescreen of a device, providing users with quicker access and a richer experience.

It would be nice if you could implement a:

1. 'multi-delete-state' which makes it possible for the user to mark which ones to delete and then a single button that deletes all the marked/highlighted notes. Currently the user must manually delete every single note created one at a time

2. You could also consider a 'Delete all notes' button :)

When editing a note, is it intentional that you're not actually editing the note created, but the 'placeholder' note which then applies the changes to the note.

My suggestion would be if you've got time, to see if you could change the logic in such a way, that when you edit a created note, the editing happens on the note in which you initiate the editing. So when a user clicks the 'pen' icon on a note, then you edit from the note where the 'pen' is located and not the 'placeholder' note at the top of the screen.

What do you think?

@curiousGeekAyon

When you have created a couple of notes and if the user then clicks on the '+'-symbol without adding text to any of the input fields, the page seems to reload/refresh and deletes all existing notes created. Im guessing this is a bug? :)

Also consider saving the user's notes so that they won't dissapear as soon as they close their browser tab/window. This can either be done by keeping the note's data in a database and fetching the user's data (this requires a lot of work as you need to implement a login-feature as well) alternatively, you could save the note data on the user's local storage OR session storage depending on your needs

Session storage
sessionStorage.setItem("lastname", "Smith");
sessionStorage.getItem("lastname");