P2 Breathe color contrast issues

[poena]

There are some remaining links in the theme that have a contrast ratio
that is lower than 4.5:1 which is needed to follow the WCAG 2.1 color contrast recommendations (​https://www.w3.org/TR/WCAG21/#contrast-minimum).
These links are also missing a underline or other kind of text decoration.

The color 888 only has a contrast ratio of 3.54:1 against the white background.
(And the size of the text means it cannot pass as large text which only requires a contrast ratio of 3:1)

In the main stylesheet, line 561 and forward:

.entry-meta .entry-date, .entry-meta .entry-actions, 
.entry-meta .entry-tags, .comment-meta .comment-date, 
.comment-meta .comment-actions {
    font-size: 0.8em;
    font-weight: 300;
    line-height: 1.2;
    color: #888888;
}

The color needs to be updated to something darker, for example 555 which is used for the main text.

---

The comment reply count text inside the button uses the color 999999,
and only has a contrast ratio of 2.68:1 against the light grey color which is the background for the button, f8f8f8.

The class name is o2-reply-count and the file that styles this is
o2/modules/post-actions/css/style.css (line 489), so it could be changed there.

Changing the text color to 666 would match it to the Reply text in the button and pass the contrast.

[coffee2code]

In 9205:

Breathe: Improve font color contrasts.

Props poena.
Fixes #4666.