Default examples to mainnet

[chadyj]

Several wallets have been testing https://react-app.walletconnect.com/ but have complained that it doesn't work.

After doing some digging it turns out they were trying to connect to a testnet, since the examples default to this.

To fix this, can we simply default to mainnet? It will hopefully help developers.

[wayne-yu-anchorage]

Hmm. I'd argue the other way around: since https://react-app.walletconnect.com/ is meant for testing only, it's better to default to TestNets since that would likely be the bulk of cases.

Besides, defaulting to Mainnets would similarly confusing users who do intend to use TestNets.

My 2 cents :)