Add unfollow modal (optional) (#4246)

* Add unfollow modal

* unfollowing someone

* remove unnecessary prop

app/javascript/mastodon/locales/defaultMessages.json

@@ -228,6 +228,19 @@
     ],
     "path": "app/javascript/mastodon/components/video_player.json"
   },
+  {
+    "descriptors": [
+      {
+        "defaultMessage": "Unfollow",
+        "id": "confirmations.unfollow.confirm"
+      },
+      {
+        "defaultMessage": "Are you sure you want to unfollow {name}?",
+        "id": "confirmations.unfollow.message"
+      }
+    ],
+    "path": "app/javascript/mastodon/containers/account_container.json"
+  },
   {
     "descriptors": [
       {
@@ -268,6 +281,10 @@
   },
   {
     "descriptors": [
+      {
+        "defaultMessage": "Unfollow",
+        "id": "confirmations.unfollow.confirm"
+      },
       {
         "defaultMessage": "Block",
         "id": "confirmations.block.confirm"
@@ -280,6 +297,10 @@
         "defaultMessage": "Hide entire domain",
         "id": "confirmations.domain_block.confirm"
       },
+      {
+        "defaultMessage": "Are you sure you want to unfollow {name}?",
+        "id": "confirmations.unfollow.message"
+      },
       {
         "defaultMessage": "Are you sure you want to block {name}?",
         "id": "confirmations.block.message"