Enhance Readability and Structure of Simple Calendar README

[lrazcs]

This pull request focuses on improving the readability and structure of the Simple Calendar README. The changes include reorganizing content into clear sections, updating the formatting for a more modern look, and refining the language to provide concise and user-friendly information. The goal is to make it easier for users to understand the app's features, benefits, and how to get started. The revised README now features a table of contents, categorized features, a simplified introduction, and a cleaner visual presentation.

[inson1]

@lrazcs SMT apps were sold to ad company. Fork is here https://github.com/FossifyOrg

[chloeimb]

I see that there is a new fork with a new repository, but your read me changes look good. I can tell that good effort was made.