get alchemy provider api url from env and use it to get provider

Co-authored-by: brunoedcf <brest.dallacosta@outlook.com>

.env.example

@@ -1,3 +1,3 @@
 VITE_API_URL=http://localhost:8000/
-VITE_GOERLI_API_KEY={GOERLI_API_KEY_ALCHEMY}
-VITE_MUMBAI_API_KEY={MUMBAI_API_KEY_ALCHEMY}
+VITE_GOERLI_API_URL={GOERLI_API_URL_ALCHEMY}
+VITE_MUMBAI_API_URL={MUMBAI_API_URL_ALCHEMY}