frontend for multiple hotkeys for each command

The options UI can now handle setting and deleting multiple hotkeys for each command

css/options.css

@@ -120,6 +120,10 @@ hr {
   margin: 6px 10px;
 }
 
+.hotkeys {
+  margin: 0 4px;
+}
+
 .hotkeys .btn-text {
   margin-right: 0;
 }
@@ -130,6 +134,7 @@ hr {
 
 .btn-enter {
   background-color: #00b1e2;
+  margin-left: auto;
 }
 
 .reset-area {
@@ -202,3 +207,15 @@ hr {
   border-radius: 8px;
   box-shadow: 0 0 0 2px rgba(255, 255, 255, 0.1);
 }
+
+.addHotkey {
+  opacity: 0;
+  margin-left: auto;
+  margin-right: 4px;
+  transition: opacity 0.4s ease-out;
+}
+
+.setting:hover .addHotkey {
+  opacity: 1;
+  transition: opacity 0.2s linear;
+}