Chore: Setup Netlify CORS

https://docs.blockstack.org/develop/zero_to_dapp_3.html#go-live-on-the-internet

Author: benoror

public/_headers

@@ -0,0 +1,8 @@
+/index.html
+  Access-Control-Allow-Origin: *
+  Access-Control-Allow-Headers: "X-Requested-With, Content-Type, Origin, Authorization, Accept, Client-Security-Token, Accept-Encoding"
+  Access-Control-Allow-Methods: "POST, GET, OPTIONS, DELETE, PUT"
+/manifest.json
+  Access-Control-Allow-Origin: *
+  Access-Control-Allow-Headers: "X-Requested-With, Content-Type, Origin, Authorization, Accept, Client-Security-Token, Accept-Encoding"
+  Access-Control-Allow-Methods: "POST, GET, OPTIONS, DELETE, PUT"

public/_redirects

@@ -0,0 +1 @@
+/* /index.html 200