fix: dont export json conversions of jsonrpc (#44)

ethers/providers/jsonrpc.nim

@@ -9,9 +9,9 @@ import ../signer
 import ./jsonrpc/rpccalls
 import ./jsonrpc/conversions
 
+export json
 export basics
 export provider
-export conversions
 
 push: {.upraises: [].}
 

testmodule/testJsonRpcProvider.nim

@@ -2,6 +2,7 @@ import std/json
 import pkg/asynctest
 import pkg/chronos
 import pkg/ethers
+import pkg/ethers/providers/jsonrpc/conversions
 import pkg/stew/byteutils
 import ./examples
 import ./miner