update Safe Apps monorepo README with project overview and package re…#653

thegoodeth12 wants to merge 1 commit intosafe-global:mainsafe-global/safe-apps-sdk:mainfrom

Safe-Wallet-Custom-Secure-dApp:Safe-wallet-custom-secure-dApp/safe-apps-sdkSafe-Wallet-Custom-Secure-dApp/safe-apps-sdk:Safe-wallet-custom-secure-dApp/safe-apps-sdkCopy head branch name to clipboard