improved: Gap between header and first image

[math-GH]

In some rare cases the first image is not wrapped into a <p> so that there is no gap between the header and the image (the <p> has some margin).

Before:

After:

Changes proposed in this pull request:

• padding-bottom added

How to test the feature manually:

1. a useful feed could be: https://gizmodo.com/rss
2. normal view/reading view
3. see the gap over the image

Pull request checklist:

• clear commit messages
• code manually tested

[Frenzie]

And when there's a <p> with margin the margins collapse I presume?