feat: drop serverlessv2 drop

BREAKING CHANGE: v3.0.0 required

Author: horike37

README.md

@@ -881,4 +881,4 @@ custom:
                 "success": false,
                 "errorMessage": "Client Error"
               }
-```
+```

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "serverless-apigateway-service-proxy",
-  "version": "1.15.0",
+  "version": "2.0.0",
   "description": "The Serverless Framewrok plugin for supporting AWS service proxy integration of API Gateway",
   "main": "lib/index.js",
   "scripts": {
@@ -59,7 +59,7 @@
     "node-fetch": "^2.6.0",
     "nyc": "^15.1.0",
     "prettier": "^1.18.2",
-    "semantic-release": "^17.2.3",
+    "semantic-release": "^17.4.7",
     "serverless": "^3.7.5",
     "sinon": "^7.3.2",
     "sinon-chai": "^3.3.0"