Add Japanese translations (pin) (#3551)

* Add Japanese translations (pin)

* "ピン留め" is more general

app/javascript/mastodon/locales/defaultMessages.json

@@ -51,6 +51,23 @@
     ],
     "path": "app/javascript/mastodon/components/column_back_button.json"
   },
+  {
+    "descriptors": [
+      {
+        "defaultMessage": "Unpin",
+        "id": "column_header.unpin"
+      },
+      {
+        "defaultMessage": "Pin",
+        "id": "column_header.pin"
+      },
+      {
+        "defaultMessage": "Back",
+        "id": "column_back_button.label"
+      }
+    ],
+    "path": "app/javascript/mastodon/components/column_header.json"
+  },
   {
     "descriptors": [
       {
@@ -657,6 +674,14 @@
         "defaultMessage": "Getting started",
         "id": "getting_started.heading"
       },
+      {
+        "defaultMessage": "Home",
+        "id": "tabs_bar.home"
+      },
+      {
+        "defaultMessage": "Notifications",
+        "id": "tabs_bar.notifications"
+      },
       {
         "defaultMessage": "Federated timeline",
         "id": "navigation_bar.public_timeline"