Update some of the ingame screenshots

[MustaphaTR]

https://github.com/OpenRA/OpenRAWeb/blob/master/content/images/screenshots/cnc-squad.png
Shows an airstrike with just 1 plane.

https://github.com/OpenRA/OpenRAWeb/blob/master/content/images/screenshots/d2k-starport.png
Outpost offset has been fixed a long time ago.

https://github.com/OpenRA/OpenRAWeb/blob/master/content/images/screenshots/ra-allies02.png
Campaign colors.

[anjew175]

I have been looking through the newsposts for screenshots to update the front page and there is quite a few options to update with. Ill link a few I think may be fitting, would be nice if people pointed out what they thought would be good.

https://github.com/OpenRA/OpenRAWeb/blob/master/content/images/news/20161015-td-burningtrees.png
not sure if zoomed in is better or zoomed out
https://github.com/OpenRA/OpenRAWeb/blob/master/content/images/news/20160904-cnc-burningtrees.png

https://github.com/OpenRA/OpenRAWeb/blob/master/content/images/news/20180610-hinds.png
may be retconned but there it is

https://github.com/OpenRA/OpenRAWeb/blob/master/content/images/news/20170722-td-buildinghitshapes.png

https://github.com/OpenRA/OpenRAWeb/blob/master/content/images/news/20170421-ra-gapgen.png

Looking for any nice d2k pictures as well, there isnt too many in the newspost that scream action

Also looking into implementing gifs longer than 4 seconds, such as: https://github.com/OpenRA/OpenRAWeb/blob/master/content/images/news/20190106-dog-attack.gif

but that may be a topic for #123

btw im curious whats wrong with https://github.com/OpenRA/OpenRAWeb/blob/master/content/images/screenshots/ra-allies02.png