Improve 404 Page: Enhanced Search Functionality and Close Matches for Broken Docs Links

[SurajSanap]

• Increased the prominence of the "404" header using a mixture of Black (#2b3137) and Green (#2dba4e) colors.
• Styled the search bar to resemble GitHub's design with clear input and button elements.
• Removed the default value from the search box for a cleaner user experience.

Closes: #1347