fix: add repository metadata for npm provenance (#151)

Author: bnimit

package.json

@@ -4,6 +4,12 @@
   "author": "Re:Earth contributors <community@reearth.io>",
   "license": "Apache-2.0",
   "description": "A library that abstracts a map engine as one common API.",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/reearth/core.git"
+  },
+  "homepage": "https://github.com/reearth/core#readme",
+  "bugs": "https://github.com/reearth/core/issues",
   "type": "module",
   "main": "dist/core.umd.cjs",
   "module": "dist/core.js",