add missing i18n for sidebar

src/inc/locales/de.json

@@ -418,6 +418,10 @@
   },
   "sidebar": {
     "loading_activity": "Aktivität wird geladen...",
+    "no_activity": "Keine kürzliche Aktivität.",
+    "failed_to_load": "Laden fehlgeschlagen.",
+    "loading_more": "Laden…",
+    "end_of_activity": "─ Ende der Aktivität ─",
     "view": "Ansehen",
     "read_more": "mehr sehen",
     "see_less": "weniger anzeigen",

src/inc/locales/en.json

@@ -422,6 +422,10 @@
   },
   "sidebar": {
     "loading_activity": "Loading activity...",
+    "no_activity": "No recent activity.",
+    "failed_to_load": "Failed to load.",
+    "loading_more": "Loading…",
+    "end_of_activity": "─ end of activity ─",
     "view": "View",
     "read_more": "read more",
     "see_less": "see less",

src/inc/locales/nl.json

@@ -418,6 +418,10 @@
   },
   "sidebar": {
     "loading_activity": "Activiteit laden...",
+    "no_activity": "Geen recente activiteit.",
+    "failed_to_load": "Laden mislukt.",
+    "loading_more": "Laden…",
+    "end_of_activity": "─ einde van activiteit ─",
     "view": "Bekijken",
     "read_more": "lees meer",
     "see_less": "zie minder",

src/inc/locales/zange.json

@@ -419,6 +419,10 @@
   },
   "sidebar": {
     "loading_activity": "Aktivität wird geladen...",
+    "no_activity": "Noch keine Aktivität",
+    "failed_to_load": "Ladung gescheitert.",
+    "loading_more": "Ladung wird aufbereitet…",
+    "end_of_activity": "─ Ende des Aktivitätsfadens ─",
     "view": "Ansehen",
     "read_more": "mehr sehen",
     "see_less": "weniger sehen",