Add payable to the README example (#35)

* Add payable to the README example

* Update the method casing

Author: ali-behjati

README.md

@@ -31,9 +31,9 @@ contract ExampleContract {
     pyth = IPyth(pythContract);
   }
 
-  function getBTCUSDPrice(
+  function getBtcUsdPrice(
     bytes[] calldata priceUpdateData
-  ) public returns (PythStructs.Price memory) {
+  ) public payable returns (PythStructs.Price memory) {
     // Update the prices to the latest available values and pay the required fee for it. The `priceUpdateData` data
     // should be retrieved from our off-chain Price Service API using the `pyth-evm-js` package.
     // See section "How Pyth Works on EVM Chains" below for more information.