Merge pull request #457 from BitGo/WP-2200-add-avaxc-broadcast-readme

docs(root): add avax-c broadcast tx readme

AVAX-C.md

@@ -0,0 +1,19 @@
+Broadcast a transaction to the Avalanche C-Chain (AVAX-C) by constructing an API request to a full node RPC endpoint.
+
+```shell
+export REQUEST_URL="<REQUEST_URL>"
+  # Testnet: https://api.avax-test.network/ext/bc/C/rpc
+  # Mainnet: https://api.avax.network/ext/bc/C/rpc
+  # Full node RPC endpoints: https://docs.avax.network/tooling/rpc-providers
+
+curl -X POST $REQUEST_URL \
+  -H "Content-Type: application/json" \
+  -d '{
+    "id": 1,
+    "jsonrpc": "2.0",
+    "method": "eth_sendRawTransaction",
+    "params": ["0x + tx"]
+  }'
+  # find "tx" in your downloaded JSON
+  # add the “0x” prefix to the “tx” if it's not already present
+```