Revert "Remove buffer" (#15)

* Revert "Remove buffer (#14)"

This reverts commit 28e2c3b.

* Update package.json

Author: JinIgarashi

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@watergis/terrain-rgb",
-  "version": "1.1.10",
+  "version": "1.1.11",
   "description": "This module is to get elevation from terrain RGB tilesets by longitude and latitude.",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",
@@ -49,6 +49,7 @@
   "dependencies": {
     "@canvas/image-data": "^1.0.0",
     "axios": "^0.21.1",
+    "buffer": "^6.0.3",
     "pako": "^2.0.4",
     "webp-hero": "0.0.0-dev.27"
   },

package.json

@@ -1,5 +1,6 @@
 import axios from 'axios';
 import { WebpMachine, loadBinaryData } from 'webp-hero';
+import { Buffer } from 'buffer';
 import PNG from '../png';
 import * as tilebelt from '../tilebelt';