plugins/README: fix syntax highlighting
plugins/README: fix syntax highlighting

jagan-veeraraghavan/svgo,ben-eb/svgo,svg/svgo,svg/svgo,WebTwist/svgo,bORm/svgo,subzey/svgo,pieter-lazzaro/svgo,akatopo/svgo,OrangeLV/svgo,ennett50/svgo,PeterWangPo/svgo,pgherveou/svgo,ricardobeat/svgo,allypalanzi/svgo