[FEATURE] Polish and improve README readability

### Brief summary

Improve the readability and formatting of the project README.md to make it more welcoming for new open-source contributors.

### Motivation

The README is the first thing visitors see when they land on the repo. Making it easier to read and more visually clear helps new contributors quickly understand what Splitt is and how to get involved. A polished README is vital for our community!

### Acceptance criteria

[ ] Add relevant emojis to the main section headings.

[ ] Break up any long, dense paragraphs into shorter 2-3 sentence blocks.

[ ] Ensure the "Tech Stack" and "Setup" sections use clear bullet points or bold text for readability.

[ ] Verify that all existing markdown syntax (links, code blocks) renders correctly without errors.

### Proposed design

README.md

### Out of scope

Taking or adding screenshots. Adding CI badges. Changing the actual core content, meaning, or structure significantly, this is about visual polish and formatting, not a total rewrite!