adds customizable "about" section

web/src/lib/i18n/locales/zh.json

@@ -178,6 +178,7 @@
   "gas-station": "",
   "german": "德语",
   "get-position-from-exif": "从EXIF数据获取坐标",
+  "get-started": "",
   "grid": "网格",
   "grocery-store": "",
   "heading": "Heading",
@@ -320,6 +321,7 @@
   "radius": "半径",
   "railway-station": "",
   "read-more": "阅读更多",
+  "ready-to-join": "",
   "recalculate-elevation-data": "",
   "recalculating-elevation-data-hint": "",
   "register": "注册",