feat(dropdown): support readonly variant

The read-only checkbox still changed their cursor on hover confusing the user one could still change it.
While doing it i added support for read-only to the dropdown component as well

Removed cursor changes for read-only checkbox
Added "read-only" variant to dropdown similar to the existing variant for checkbox

src/definitions/modules/checkbox.less

@@ -349,14 +349,16 @@
   color: @checkboxActiveFocusCheckColor;
 }
 
+& when (@variationCheckboxReadonly) {
+  /*--------------
+      Read-Only
+  ---------------*/
 
-/*--------------
-    Read-Only
----------------*/
-
-.ui.read-only.checkbox,
-.ui.read-only.checkbox label {
-  cursor: default;
+  .ui.read-only.checkbox,
+  .ui.read-only.checkbox label {
+    cursor: default;
+    pointer-events: none;
+  }
 }
 
 & when (@variationCheckboxDisabled) {
@@ -366,7 +368,7 @@
 
   .ui.disabled.checkbox label,
   .ui.checkbox input[disabled] ~ label {
-    cursor: default !important;
+    cursor: default;
     opacity: @disabledCheckboxOpacity;
     color: @disabledCheckboxLabelColor;
     pointer-events: none;

src/definitions/modules/dropdown.less

@@ -1135,6 +1135,16 @@ select.ui.dropdown {
   }
 }
 
+& when (@variationDropdownReadonly) {
+  /*--------------------
+          Read-Only
+  ----------------------*/
+
+  .ui.read-only.dropdown {
+    cursor: default;
+    pointer-events: none;
+  }
+}
 
 /*******************************
            Variations

src/themes/default/globals/variation.variables

@@ -378,6 +378,7 @@
 /* Checkbox */
 @variationCheckboxBox: false;   //.box (instead of label) is an ancient fragment of sui v1 and not even documented in v2.x anymore
 @variationCheckboxDisabled: true;
+@variationCheckboxReadonly: true;
 @variationCheckboxInverted: true;
 @variationCheckboxRadio: true;
 @variationCheckboxSlider: true;
@@ -401,6 +402,7 @@
 /* Dropdown */
 @variationDropdownInverted: true;
 @variationDropdownDisabled: true;
+@variationDropdownReadonly: true;
 @variationDropdownLabel: true;
 @variationDropdownButton: true;
 @variationDropdownSelection: true;