feat(player): a video's related videos, on demand beside it

The player shows what YouTube lists beside the video, without what the
user has watched or hidden. Wide, a Related tab beside the description;
stacked, a button beside the info opens them in a drawer. A row plays in
the same player (Back returns) and the list stays the opened video's.
A switch picks on-topic or Hungarian-trending lists, kept on the account.

Each related row says whether the user follows its channel; the row is
the video card's narrow form with its whole menu. VideoMenu moves to
features/video, where the player can reach it.

frontend/src/i18n/locales/en/player.json

@@ -26,6 +26,18 @@
   "descriptionFailed": "Couldn't load the description",
   "descriptionMore": "More",
   "descriptionLess": "Less",
+  "panelTabs": "Video details",
+  "related": {
+    "title": "Related",
+    "region": "Which related videos",
+    "topical": "On topic",
+    "hu": "Hungarian trending",
+    "followed": "You follow this channel",
+    "empty": "No related videos you haven't seen yet.",
+    "error": "Couldn't load the related videos",
+    "more": "Show more",
+    "loading": "Loading…"
+  },
   "collapsePanel": "Hide the details",
   "expandPanel": "Show the details",
   "channel": "Channel",

frontend/src/i18n/locales/hu/player.json

@@ -26,6 +26,18 @@
   "descriptionFailed": "Nem sikerült betölteni a leírást",
   "descriptionMore": "Több",
   "descriptionLess": "Kevesebb",
+  "panelTabs": "A videó részletei",
+  "related": {
+    "title": "Kapcsolódók",
+    "region": "Milyen kapcsolódó videók",
+    "topical": "Témába vágó",
+    "hu": "Magyar trend",
+    "followed": "Követed ezt a csatornát",
+    "empty": "Nincs olyan kapcsolódó videó, amit még nem láttál.",
+    "error": "Nem sikerült betölteni a kapcsolódó videókat",
+    "more": "Mutass többet",
+    "loading": "Betöltés…"
+  },
   "collapsePanel": "Részletek elrejtése",
   "expandPanel": "Részletek megjelenítése",
   "channel": "Csatorna",