CustomCategory: add a close button

lang/en.json

@@ -6,6 +6,7 @@
     "cancel": "Cancel",
     "categories": "Categories",
     "category-info-tooltip": "Info & Map key",
+    "close": "Close",
     "closed": "closed",
     "default": "default",
     "apply": "Apply",

src/customCategory.js

@@ -117,6 +117,12 @@ class CustomCategoryEditor {
     input.value = lang('apply')
     controls.appendChild(input)
 
+    const inputClose = document.createElement('input')
+    inputClose.type = 'button'
+    inputClose.value = lang('close')
+    inputClose.onclick = () => this.window.close()
+    controls.appendChild(inputClose)
+
     const tutorial = document.createElement('span')
     tutorial.className = 'tip-tutorial'
     let text = lang('tip-tutorial')