added more warnings

Author: NishithPat

.gitignore

@@ -1,3 +1,4 @@
 .secret
 .env
 node_modules
+.DS_Store

client/src/App.js

@@ -169,6 +169,9 @@ function App() {
           <Box mt="1.5rem">
             <Typography variant="h5" align="center">Loading Web3, accounts, and contract...</Typography>
           </Box>
+          <Box mt="1.5rem">
+            <Typography variant="h5" align="center">Please use the rinkeby testnet. If you are using another network, then please switch over to rinkeby and refresh the page!</Typography>
+          </Box>
           <Box mt="2rem" component="span">
             <Typography variant="h6" align="center">If you do not have an etherum wallet, you can install it from here: </Typography>
           </Box>