[phpcs] Add check for concatenation operator spacing
[phpcs] Add check for concatenation operator spacing

The concatenation operator should have one space before and after

ORelio/rss-bridge,Riduidel/rss-bridge,RSS-Bridge/rss-bridge,sebsauvage/rss-bridge,ORelio/rss-bridge,kranack/rss-bridge,Frenzie/rss-bridge,kranack/rss-bridge,kranack/rss-bridge,Frenzie/rss-bridge,ORelio/rss-bridge,Riduidel/rss-bridge,RSS-Bridge/rss-bridge,simonbru/rss-bridge,RSS-Bridge/rss-bridge,Riduidel/rss-bridge,simonbru/rss-bridge,kranack/rss-bridge