Log notes on how to set up AWS S3 for Uppy from scratch (draft)

examples/aws-nodejs/from-scratch-with-sts.md

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+Assuming you have MY-UPPY-USER and MY-UPPY-BUCKET, here’s how you can allow MY-UPPY-USER to get STS Federated Token and upload files to MY-UPPY-BUCKET:
+
+1. Set CORS settings on `MY-UPPY-BUCKET` bucket:
+
+    ```json
+    [
+        {
+            "AllowedHeaders": [
+                "*"
+            ],
+            "AllowedMethods": [
+                "GET",
+                "PUT",
+                "HEAD",
+                "POST",
+                "DELETE"
+            ],
+            "AllowedOrigins": [
+                "*"
+            ],
+            "ExposeHeaders": [
+                "ETag",
+                "Location"
+            ]
+        }
+    ]
+    ```
+
+2. Add a Policy to `MY-UPPY-BUCKET`:
+
+    ```json
+    {
+        "Version": "2012-10-17",
+        "Statement": [
+            {
+                "Sid": "MyMultipartPolicyStatement1",
+                "Effect": "Allow",
+                "Principal": {
+                    "AWS": "arn:aws:iam::*:user/MY-UPPY-USER"
+                },
+                "Action": [
+                    "s3:PutObject",
+                    "s3:ListMultipartUploadParts",
+                    "s3:AbortMultipartUpload"
+                ],
+                "Resource": "arn:aws:s3:::MY-UPPY-BUCKET/*"
+            }
+        ]
+    }
+    ```
+
+3. Add a Policy to `MY-UPPY-USER`:
+
+    **Optional** if you’d like to enable signing on the client:
+
+    ```json
+    {
+        "Version": "2012-10-17",
+        "Statement": [
+            {
+                "Sid": "MyStsPolicyStatement1",
+                "Effect": "Allow",
+                "Action": [
+                    "sts:GetFederationToken"
+                ],
+                "Resource": [
+                    "arn:aws:sts::*:federated-user/*"
+                ]
+            }
+        ]
+    }
+	```