ERC20: return bool from transfer/transferFrom/approve (EIP-20)

[aapsi]

Description

Align ERC20Facet with the ERC‑20 ABI by making transfer, transferFrom, and approve return bool and return true on success.

Why

• EIP‑20 specifies returns (bool) for these functions.
• Improves compatibility with wallets, routers, and typed bindings that expect the canonical ABI.
• No behavioral change: functions already revert on failure; this makes success explicit.

Changes

• approve(address,uint256) external returns (bool) → returns true on success
• transfer(address,uint256) external returns (bool) → returns true on success
• transferFrom(address,address,uint256) external returns (bool) → returns true on success
• No storage or logic changes; libraries unchanged.

Notes

• If standardize internal function names #43 touches ERC20Facet, I’ll rebase to adopt any internal rename.

[mudgen]

@aapsi Good point. I checked and OpenZeppelin has these functions return bool too. @aapsi thanks for submitting this pull request.