add initial readme and logo

Author: bartolomej

topics/flow-blockchain/flow.png

@@ -0,0 +1,12 @@
+---
+created_by: Flow
+display_name: Flow blockchain
+logo: flow.png
+released: Sep 29, 2020
+short_description: Flow is permissionless layer 1 blockchain.
+topic: flow-blockchain
+related: blockchain, cryptocurrency
+url: https://flow.com
+github_url: https://github.com/onflow
+---
+A permissionless layer 1 blockchain, empowering developers to create limitless Web3 apps for mainstream adoption.