Align announcement bar with theme colors for consistency and clear visibility(keploy/Docs #3002).

[Gouravjaat07]

What has changed?

1. Announcement Banner Styling

   • Current Behavior: The announcement banner was displayed in plain white, making it hard to notice and visually inconsistent with the rest of the docs.
   • Expected Behavior: The banner now uses the docs theme colors, with a blue background (#1E73E8) and white text (#FFFFFF), making it consistent, attractive, and easily noticeable.
   • Steps Taken: Updated the CSS in custom.css to apply the correct background and text colors.

2. Docusaurus Start Issue

   • Fixed the 'docusaurus' is not recognized as an internal or external command error.
   • Steps Taken: Installed the latest Docusaurus packages locally:

     npm install @docusaurus/core@latest @docusaurus/preset-classic@latest
     

     Then started the dev server using:

     npx docusaurus start
     

This PR Resolves #(3002)

Type of change

• [x] Bug fix (non-breaking change which fixes an issue).
• [x] Style update (non-breaking visual change that improves UI/UX).

How Has This Been Tested?

• Run npx docusaurus start and confirmed the dev server starts without errors.
• Verified the announcement banner displays correctly on the website.
• Checked overall styling to ensure it follows the project guidelines.

Before fixing issue :

After fixing issue :

Checklist:

• [x] My code follows the style guidelines of this project.
• [x] I have performed a self-review of my own code.

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