Mobile wizard layout (all steps) on new bug form

[munteanu210]

Implement the wizard layout and content for the main categories, all sub-categories, browser & device selection, following the mobile UI/UX on the new bug form.

[karlcow]

Does that mean there are two different versions for desktop and mobile? Instead of one responsive version?

[miketaylr]

@munteanu210 ^^

[munteanu210]

Does that mean there are two different versions for desktop and mobile? Instead of one responsive version?

@karlcow, there is a single version. The mobile view is all about style updates that make the page responsive.

[munteanu210]

I fixed this issue in this commit which is a part of PR #2938. The commit may seem large, but the updates are minor. For example, it adds classes to the elements so that they have specific behavior on mobile. Also, I changed the CSS to be mobile-first as seen on the project. This being said, a large block of desktop overrides was added.