Fix up schema and template

Author: louisgv

keys.schema.json

@@ -38,6 +38,10 @@
           "type": "string",
           "description": "See: https://github.com/PlasmoHQ/chrome-webstore-api/blob/main/token.md"
         },
+        "clientSecret": {
+          "type": "string",
+          "description": "See: https://github.com/PlasmoHQ/chrome-webstore-api/blob/main/token.md"
+        },
         "zip": {
           "type": "string"
         },
@@ -48,7 +52,7 @@
           "default": "default"
         }
       },
-      "required": ["extId", "refreshToken", "clientId"]
+      "required": ["extId", "refreshToken", "clientId", "clientSecret"]
     },
     "Firefox": {
       "type": "object",

keys.template.json

@@ -2,6 +2,7 @@
   "$schema": "https://raw.githubusercontent.com/plasmo-corp/bpp/v2/keys.schema.json",
   "chrome": {
     "clientId": "123",
+    "clientSecret": "123",
     "refreshToken": "789",
     "extId": "abcd"
   },