Changing Background in Notes App

[AakxSha]

We need to change the background of the given app to make it more aesthetically pleasing.

Current Behavior:
We currently do not have any background
Expected Behavior:
We aim to create a visually appealing background which will also increase readability and enhance overall user experience.

I am thinking something like this for the day theme:

and something like this for the night theme:

[AakxSha]

Issue resolved! Here are the screenshots of the updated version:
Dark theme:

Light theme:

[AakxSha]

Please review the changes made

[AakxSha]

@nisha-laur can you please review and suggest changes so i can create a pr