API: Add experimental Json API

in preparation for external healthchecks and the
admin backend. We define a couple test routes:

- / List all routes
- /ping Replies pong for online-checks
- /stats Get high-level bot statistics
- /most-recent-drop Returns the most recent entry from dropHistories

The last two routes require a valid apikey header.
All routes are prefixed by /api/v1

package.json

@@ -13,9 +13,11 @@
   "dependencies": {
     "@discordjs/rest": "^0.3.0",
     "axios": "^0.27.2",
+    "body-parser": "^1.20.2",
     "discord-api-types": "^0.37.2",
     "discord.js": "^14.0.0",
     "dotenv": "^16.0.0",
+    "express": "^4.18.2",
     "mysql2": "^2.3.3",
     "nanoid": "^3.0.0",
     "nodemon": "^2.0.15",