chore: export subscriptions

This has a knock-on effect of nim-serde not being imported into subscriptions when JsonRpcProvider.new is called from a consumer that does not export nim-serde.

Author: emizzle

ethers/providers/jsonrpc.nim

@@ -17,6 +17,7 @@ export basics
 export provider
 export chronicles
 export errors.JsonRpcProviderError
+export subscriptions
 
 {.push raises: [].}