Add messages informing that collections are empty (fixes #4115) (#8418)

* Add messages informing that collections are empty

Adds empty messages to blocked users, domain blocks, favourited statuses, users
that favourited toot, follow requests, followers of given user, user's being
followed by given user, lists, muted users, toots' boosts.

Switched from using ScrollContainer to ScrollableList and/or added empty
message's text.

Fixes #4115

* Update localization files with strings for #4115

* Fix whitespace issues pointed out by codeclimate

app/javascript/mastodon/locales/defaultMessages.json

@@ -638,6 +638,10 @@
       {
         "defaultMessage": "Blocked users",
         "id": "column.blocks"
+      },
+      {
+        "defaultMessage": "You haven't blocked any users yet.",
+        "id": "empty_column.blocks"
       }
     ],
     "path": "app/javascript/mastodon/features/blocks/index.json"
@@ -1049,6 +1053,10 @@
       {
         "defaultMessage": "Unhide {domain}",
         "id": "account.unblock_domain"
+      },
+      {
+        "defaultMessage": "There are no hidden domains yet.",
+        "id": "empty_column.domain_blocks"
       }
     ],
     "path": "app/javascript/mastodon/features/domain_blocks/index.json"
@@ -1058,10 +1066,23 @@
       {
         "defaultMessage": "Favourites",
         "id": "column.favourites"
+      },
+      {
+        "defaultMessage": "You don't have any favourite toots yet. When you favourite one, it will show up here.",
+        "id": "empty_column.favourited_statuses"
       }
     ],
     "path": "app/javascript/mastodon/features/favourited_statuses/index.json"
   },
+  {
+    "descriptors": [
+      {
+        "defaultMessage": "No one has favourited this toot yet. When someone does, they will show up here.",
+        "id": "empty_column.favourites"
+      }
+    ],
+    "path": "app/javascript/mastodon/features/favourites/index.json"
+  },
   {
     "descriptors": [
       {
@@ -1080,10 +1101,32 @@
       {
         "defaultMessage": "Follow requests",
         "id": "column.follow_requests"
+      },
+      {
+        "defaultMessage": "You don't have any follow requests yet. When you receive one, it will show up here.",
+        "id": "empty_column.follow_requests"
       }
     ],
     "path": "app/javascript/mastodon/features/follow_requests/index.json"
   },
+  {
+    "descriptors": [
+      {
+        "defaultMessage": "No one follows this user yet.",
+        "id": "account.followers.empty"
+      }
+    ],
+    "path": "app/javascript/mastodon/features/followers/index.json"
+  },
+  {
+    "descriptors": [
+      {
+        "defaultMessage": "This user doesn't follow anyone yet.",
+        "id": "account.follows.empty"
+      }
+    ],
+    "path": "app/javascript/mastodon/features/following/index.json"
+  },
   {
     "descriptors": [
       {
@@ -1398,6 +1441,10 @@
       {
         "defaultMessage": "Your lists",
         "id": "lists.subheading"
+      },
+      {
+        "defaultMessage": "You don't have any lists yet. When you create one, it will show up here.",
+        "id": "empty_column.lists"
       }
     ],
     "path": "app/javascript/mastodon/features/lists/index.json"
@@ -1407,6 +1454,10 @@
       {
         "defaultMessage": "Muted users",
         "id": "column.mutes"
+      },
+      {
+        "defaultMessage": "You haven't muted any users yet.",
+        "id": "empty_column.mutes"
       }
     ],
     "path": "app/javascript/mastodon/features/mutes/index.json"
@@ -1526,6 +1577,15 @@
     ],
     "path": "app/javascript/mastodon/features/public_timeline/index.json"
   },
+  {
+    "descriptors": [
+      {
+        "defaultMessage": "No one has boosted this toot yet. When someone does, they will show up here.",
+        "id": "status.reblogs.empty"
+      }
+    ],
+    "path": "app/javascript/mastodon/features/reblogs/index.json"
+  },
   {
     "descriptors": [
       {