Embedded Wallets: missing function descriptions

As part of the first pass/pattern updates round, I added links from tables in readme files through to the configuration pages the table lists configs for. This highlighted a couple of functions that are listed without further details:

embedded-wallets/sdk/js/usage/README.mdx
`addChain()` 
`showTransactionConfirmation()` 
These are only mentioned in the README table; no page found.