Document current peculiarities
    
    - Changelog order
    - Scratch builds
    - Potential warnings and errors
    - Unexpected behavior
    - Local builds
    
    Additionally, use our own custom style sheet. Especially, we want to
    give a little more space to the left-hand sidebar since `rpmautospec`
    seems to be a little longer than what the theme allows by default.
    Having `rpmautospec` split over two lines does not look that great.
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>