feat: webshipper (#118)

* register fulfillment providers as singletons

* fix: adds subscribers/api endpoints and webhook handlers

* Adds readme

* Allow document attachments to orders:

* chore: gitignore utils

* chore: rm compiled files

packages/medusa-fulfillment-webshipper/.eslintrc

@@ -0,0 +1,9 @@
+{
+  "plugins": ["prettier"],
+  "extends": ["prettier"],
+  "rules": {
+    "prettier/prettier": "error",
+    "semi": "error",
+    "no-unused-expressions": "true"
+  }
+}