Redesign README with concise structure and safer browser-specific install guidance

[Copilot]

The repository needed a cleaner, more attractive README.md that is quick to scan and includes the required sections for adoption and contribution. This PR rewrites the README around the project’s core value proposition and clarifies browser-specific setup details.

• Documentation structure overhaul

  • Reorganized README into explicit sections:
    • Title + short description
    • Features
    • Installation (Chrome / Firefox)
    • Usage
    • Contributing
    • License
  • Removed noise and reduced redundancy to improve scanability.

• Content modernization

  • Refocused copy on Focus Flow’s primary behavior: replacing distracting feeds with inspirational quotes.
  • Kept emoji-enhanced headings and section styling for readability without adding clutter.
  • Added a centered preview image block for quick visual context.

• Installation clarity and safety

  • Preserved distinct Chrome and Firefox paths.
  • Updated Firefox instructions to explicitly back up existing manifest.json before renaming manifest_firefox.json.
  • Kept pointer to FIREFOX_INSTALLATION.md, including temporary add-on caveats/permanent install context.

### 🦊 Mozilla Firefox

1. Download or clone this repository.
2. In the project folder, back up the existing `manifest.json`, then rename `manifest_firefox.json` to `manifest.json`.
3. Open `about:debugging#/runtime/this-firefox`.
4. Click **Load Temporary Add-on**.
5. Select any file from this project folder.

Original prompt

Create a beautiful, well-structured README.md for this repository.
The README should include:

• A catchy title and short description based on: "Focus Flow is a powerful browser extension for Google Chrome & Firefox that helps you reclaim your time and attention by replacing distracting social media news feeds with clean, inspirational quotes."
• Features section
• Installation instructions (for Chrome & Firefox)
• Usage instructions
• Contributing section
• License section

Make it visually appealing using emojis, headers, and markdown features.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: Add a suitable, beautiful README in my projects specially all the projects

Assistant: I found 29 repositories under your account! Adding a beautiful README.md to all of them at once is a big task, and creating 29 pull requests simultaneously could be overwhelming.

To get started, I can help you create a beautiful, well-structured README for your most descriptive projects. Let's start by opening a Pull Request for your focus-flow-extension project, since it has a great description!

Assistant: I have set up a pull request to add a beautiful README to your focus-flow-extension repository, and I am waiting for you to accept the prompt so we can continue with this project and the rest of your repositories.

This pull request was created from Copilot chat.