add greenlock bin

package.json

@@ -1,10 +1,13 @@
 {
     "name": "@root/greenlock",
-    "version": "3.0.27",
+    "version": "3.1.0",
     "description": "The easiest Let's Encrypt client for Node.js and Browsers",
     "homepage": "https://rootprojects.org/greenlock/",
     "main": "greenlock.js",
     "browser": {},
+    "bin": {
+        "greenlock": "bin/greenlock.js"
+    },
     "files": [
         "*.js",
         "lib",
@@ -40,6 +43,7 @@
         "@root/keypairs": "^0.9.0",
         "@root/mkdirp": "^1.0.0",
         "@root/request": "^1.3.10",
+        "acme-dns-01-digitalocean": "^3.0.1",
         "acme-http-01-standalone": "^3.0.5",
         "cert-info": "^1.5.1",
         "greenlock-manager-fs": "^3.0.3",