style group-message view for tablet/desktop

src/style/main.scss

@@ -365,6 +365,7 @@
 .width-70{width: 70%;}
 .width-60{width: 60%;}
 .width-50{width: 50%;}
+.width-45{width: 45%;}
 .width-40{width: 40%;}
 .width-30{width: 30%;}
 .width-20{width: 20%;}
@@ -376,6 +377,7 @@
 .max-width-70{max-width: 70%;}
 .max-width-60{max-width: 60%;}
 .max-width-50{max-width: 50%;}
+.max-width-45{max-width: 45%;}
 .max-width-40{max-width: 40%;}
 .max-width-30{max-width: 30%;}
 .max-width-20{max-width: 20%;}