rustdoc: align .stab to the right on desktop

[dns2utf8]

The informative tags/labels/stabs have been moved to the left column to improve the mobile experience.
Now the table feels a bit crammed.

• One possibility is to increase the gaps between the symbol and the tags.
• Another is to align the tags to the right on the desktop.

Current nightly 2021-06-30

First draft for implementation

One possibility is something like this, but these rules result in stretched out:

.item-left {
    grid-column: 1;
    /* added */
    display: flex;
    justify-content: space-between;
    flex-flow: row wrap;
    width: 100%;
}

Based on: #86725 #86594
CC: @GuillaumeGomez

[GuillaumeGomez]

The more I think about it, the more I appreciate the fact that it's now close to the type and not on the item description anymore.