feat(plugin-infra): add package.json schema (#3456)

plugins/bookmark/package.json

@@ -1,6 +1,7 @@
 {
   "name": "@affine/bookmark-plugin",
   "version": "0.8.0-canary.0",
+  "description": "Bookmark Plugin",
   "affinePlugin": {
     "release": true,
     "entry": {

plugins/copilot/package.json

@@ -1,6 +1,7 @@
 {
   "name": "@affine/copilot-plugin",
   "private": true,
+  "description": "Copilot plugin",
   "affinePlugin": {
     "release": false,
     "entry": {

plugins/hello-world/package.json

@@ -1,6 +1,7 @@
 {
   "name": "@affine/hello-world-plugin",
   "private": true,
+  "description": "Hello world plugin",
   "version": "0.8.0-canary.0",
   "affinePlugin": {
     "release": false,