OO-2365 add icon for participant folder course element

src/main/webapp/static/themes/light/modules/_icons.scss

@@ -334,6 +334,7 @@ $fa-css-prefix: "o_icon" !default;
 .o_cal_icon:before { content: $fa-var-calendar; }
 .o_wiki_icon:before { content: $fa-var-globe; }
 .o_podcast_icon:before { content: $fa-var-video-camera; }
+.o_pf_icon:before { content: $fa-var-inbox; }
 .o_blog_icon:before { content: $fa-var-bullhorn; }
 .o_ep_icon:before { content: $fa-var-briefcase; }
 .o_ep_icon_v1:before { content: $fa-var-puzzle-piece; }