✨(sdk) add sdk projects

It includes a consumer project which is simply a demo app. The sdk
project includes the first version of the SDK, with a light React
implementation. The first version lays down the foundations of
the iframe sdk framework. The npm package logic is also already
ready to be published.

src/sdk/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "sdk",
+  "version": "0.0.0",
+  "author": "",
+  "license": "ISC",
+  "description": "",
+  "workspaces": [
+    "./library",
+    "./consumer"
+  ]
+}