Muxed Accounts: add a warning on current state of adoption

[tomerweller]

Maybe something like:
✅ It is safe for all wallets to implement sending to muxed accounts.
❗ If you wish to receive deposits to muxed accounts please keep in mind that they are not yet supported by all wallets and exchanges

@Shaptic @leighmcculloch thoughts?

[briwylde08]

Sounds good. Is there an easy way to figure out whether a wallet/exchange does support muxed accounts?

[leighmcculloch]

👍

[leighmcculloch]

❗ If you wish to receive deposits to muxed accounts please keep in mind that they are not yet supported by all wallets and exchanges

Let's also focus on encouraging continued support for memos in conjunction with muxed accounts, rather than discouraging use.

[briwylde08]

Added language around supporting both memos and muxed accounts and the current state of adoption (#63)