Add 'Discard Tab' for context menu

.gitignore

@@ -2,3 +2,4 @@
 src/sidebar/dist
 web-ext-artifacts
 node_modules
+package-lock.json

src/_locales/en/messages.json

@@ -72,6 +72,10 @@
     "message": "Duplicate Tab"
   },
 
+  "contextMenuDiscardTab": {
+    "message": "Discard Tab"
+  },
+
   "contextMenuMoveTabToNewWindow": {
     "message": "Move to New Window"
   },

src/_locales/zh_CN/messages.json

@@ -46,6 +46,9 @@
   "contextMenuMoveTabToNewWindow": {
     "message": "移动到新窗口"
   },
+  "contextMenuDiscardTab": {
+    "message": "中断标签页"
+  },
   "contextMenuReloadAllTabs": {
     "message": "重新载入全部标签页"
   },

src/sidebar/tabcontextmenu.js

@@ -77,6 +77,12 @@ TabContextMenu.prototype = {
         browser.tabs.duplicate(tab.id);
       }
     });
+    items.push({
+      label: browser.i18n.getMessage("contextMenuDiscardTab"),
+      onCommandFn: () => {
+        browser.tabs.discard(tab.id);
+      }
+    });
     if (this._props.canMoveToNewWindow) {
       items.push({
         label: browser.i18n.getMessage("contextMenuMoveTabToNewWindow"),