core: use common plugin-api interface

packages/fps-importer/package.json

@@ -2,7 +2,7 @@
     "name": "@hydrooj/fps-importer",
     "version": "1.3.4",
     "description": "Import FPS problems",
-    "main": "package.json",
+    "main": "index.ts",
     "repository": "https://github.com/hydro-dev/Hydro.git",
     "author": "undefined <i@undefined.moe>",
     "license": "SEE LICENSE IN LICENSE",
@@ -10,8 +10,6 @@
     "dependencies": {
         "adm-zip": "0.5.5",
         "decode-html": "^2.0.0",
-        "fs-extra": "^10.1.0",
-        "mongodb": "^3.7.3",
         "xml2js": "^0.4.23"
     },
     "devDependencies": {