feat: AWS S3 + Digitalocean Spaces storage modules (#1015)

* Provide basic implementation of AWS S3 storage module

* Abstract S3 Compatible Storage Module logic

* Refactor `getFileExtension()` into the `page` object

* Add implementation for Digitalocean storage module

* Remove accidental `async`/`await` in S3 Storage Module

* Remove argument from the call to `page.getFileExtension()`

https://github.com/Requarks/wiki/pull/1015#discussion_r321990073

server/modules/storage/digitalocean/storage.js

@@ -1,23 +1,3 @@
-module.exports = {
-  async activated() {
+const S3CompatibleStorage = require('../s3/common')
 
-  },
-  async deactivated() {
-
-  },
-  async init() {
-
-  },
-  async created() {
-
-  },
-  async updated() {
-
-  },
-  async deleted() {
-
-  },
-  async renamed() {
-
-  }
-}
+module.exports = new S3CompatibleStorage('Digitalocean')