Make use of template literals instead of string concat.

src/components/user_card_content/user_card_content.vue

@@ -63,15 +63,15 @@
       headingStyle () {
         let rgb = this.$store.state.config.colors['base00'].match(/\d+/g)
         return {
-          backgroundColor: 'rgb(' + Math.floor(rgb[0] * 0.53) + ', ' +
-                                    Math.floor(rgb[1] * 0.56) + ', ' +
-                                    Math.floor(rgb[2] * 0.59) + ')',
+          backgroundColor: `rgb(${Math.floor(rgb[0] * 0.53)},
+                                ${Math.floor(rgb[1] * 0.56)},
+                                ${Math.floor(rgb[2] * 0.59)})`,
           backgroundImage: `url(${this.user.cover_photo})`
         }
       },
       bodyStyle () {
         return {
-          background: 'linear-gradient(to bottom, rgba(0, 0, 0, 0), ' + this.$store.state.config.colors['base00'] + ' 80%)'
+          background: `linear-gradient(to bottom, rgba(0, 0, 0, 0), ${this.$store.state.config.colors['base00']} 80%)`
         }
       },
       isOtherUser () {