style: css for custom icon font

apps/app/src/styles/_fonts.scss

@@ -7,7 +7,7 @@
 .material-symbols-outlined {
   display: inline-block;
   font-family: var(--grw-font-family-material-symbols-outlined);
-  font-size: 24px;  /* Preferred icon size */
+  font-size: 24px; /* Preferred icon size */
   font-style: normal;
   font-weight: normal;
   line-height: 1;
@@ -21,3 +21,11 @@
     font-variation-settings: 'FILL' 1;
   }
 }
+
+.growi-custom-icon {
+  font-family: var(--grw-font-family-custom-icon);
+  font-size: 16px;
+  font-style: normal;
+  -webkit-font-smoothing: auto;
+  -moz-osx-font-smoothing: auto;
+}