Implement instance info endpoint (JSON, YAML, TXT) (#685)

Co-authored-by: Daniel Valentine <daniel@vielle.ws>
Co-authored-by: spikecodes <19519553+spikecodes@users.noreply.github.com>

app.json

@@ -43,6 +43,12 @@
     },
     "LIBREDDIT_SFW_ONLY": {
       "required": false
+    },
+    "LIBREDDIT_DEFAULT_HIDE_AWARDS": {
+      "required": false
+    }
+    "LIBREDDIT_BANNER": {
+      "required": false
     }
   }
 }