Port over icons from Jetpack's "Social Logos" feature

The Jetpack plugin uses "Social Logos" as a source of icons for features like its "Social Icons Widget", however, there are icons that have been added to Jetpack that are not in the main Social Logos repo (and perhaps vice-versa).

The original process was meant to be that new icons were added here in the Social Logos repo first and then pulled into Jetpack but somehow at times that process hasn't happened, so now they are out of sync.

To try and get these back in sync the two should be cross-referenced so that all icons exist in the "Social Logos".

Compare the Jetpack plugin's Social Logos implementation with the main Social Logos repository, inventory icons that exist in one but not the other, and identify the appropriate icon assets to port. Done means both collections contain the same icons; confirm the result by repeating the cross-reference.

Written by the indexing model from the issue text.