Background color for <code> elements

[VSharapov]

element {
    background-color: #7777;
    padding: 2px;
}

This ↑ looks good for small spans, but has clunky overlap when they're near. Adding the same to <pre> doesn't help. Gotta think of something elegant.

[VSharapov]

This makes the first line in a code block over-indent a bit
e.g. line 1 will be a bit to the right of line 2:

```
line1
line2
```