Issue 3445438: Styled the header.

I designed the navbar, starting by placing the site branding in the header. In the primary menu, I included the Main Navigation and Search in the block layout. Then, in the page.html.twig file, I structured the header. I assigned widths to both the logo and the menus as needed, using Bootstrap classes, and wrapped the entire header in a container. I then removed unnecessary code from the main menu’s twig template. I provided space for the search menu in the header according to the design. After that, I updated the CSS code to match the design and also updated it for responsive sizes.