Add `theme-color` meta tag to Minerva

For non-web-apps we can still control the color of the address and
status bar. Currently this is defined in MobileFrontend)
but is configurable if we ever want to change it. If not defined
(e.g. no MobileFrontend/no config) it is not added.

Bug: T204691
Depends-On: I39c0905f86edc4f52235b905850c31257e7f792e
Change-Id: I3ab0f538fb6ae3332574fd212eea1a7ec6a397bd

includes/skins/SkinMinerva.php

@@ -130,6 +130,11 @@ class SkinMinerva extends SkinTemplate {
 		$out->addMeta( 'viewport', 'initial-scale=1.0, user-scalable=yes, minimum-scale=0.25, ' .
 				'maximum-scale=5.0, width=device-width'
 		);
+		// T204691
+		$theme = $out->getConfig()->get( 'MFManifestThemeColor' );
+		if ( $theme ) {
+			$out->addMeta( 'theme-color', $theme );
+		}
 
 		// Generate skin template
 		$tpl = parent::prepareQuickTemplate();