Fix modal padding and margin to properly centre dialogs
Fix modal padding and margin to properly centre dialogs

mattgodbolt/compiler-explorer,dkm/gcc-explorer,dkm/gcc-explorer,dkm/gcc-explorer,mattgodbolt/compiler-explorer,dkm/gcc-explorer,dkm/gcc-explorer,mattgodbolt/gcc-explorer,mattgodbolt/gcc-explorer,mattgodbolt/gcc-explorer,dkm/gcc-explorer,dkm/gcc-explorer,mattgodbolt/compiler-explorer,mattgodbolt/compiler-explorer,mattgodbolt/compiler-explorer,mattgodbolt/gcc-explorer,mattgodbolt/compiler-explorer,dkm/gcc-explorer,mattgodbolt/compiler-explorer,dkm/gcc-explorer,mattgodbolt/compiler-explorer,mattgodbolt/gcc-explorer