docs: document EmbeddedWallet automatic gas estimation and private authwits#21790

critesjosh wants to merge 1 commit intonextAztecProtocol/aztec-packages:nextfrom

josh/ecodr-889-update-docs-around-new-embeddedwallet-featuresAztecProtocol/aztec-packages:josh/ecodr-889-update-docs-around-new-embeddedwallet-featuresCopy head branch name to clipboard