Apply changes based on ECH call ethereum#5

Applied the changes based on feedback received on the EIP Editing Office
Hour Meeting ethereum#5.

This commit includes changes to the proposal as well as adds an exaple
implementation to assets/ directory.

assets/eip-5773/contracts/IMultiResource.sol

@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: Apache-2.0
+
+pragma solidity ^0.8.0;
+
+interface IMultiResource {
+    event ResourceSet(uint64 resourceId);
+
+    event ResourceAddedToToken(
+        uint256 indexed tokenId,
+        uint64 indexed resourceId,
+        uint64 indexed overwritesId
+    );
+
+    event ResourceAccepted(
+        uint256 indexed tokenId,
+        uint64 indexed resourceId,
+        uint64 indexed overwritesId
+    );
+
+    event ResourceRejected(uint256 indexed tokenId, uint64 indexed resourceId);
+
+    event ResourcePrioritySet(uint256 indexed tokenId);
+
+    event ApprovalForResources(
+        address indexed owner,
+        address indexed approved,
+        uint256 indexed tokenId
+    );
+
+    event ApprovalForAllForResources(
+        address indexed owner,
+        address indexed operator,
+        bool approved
+    );
+
+    function acceptResource(
+        uint256 tokenId,
+        uint256 index,
+        uint64 resourceId
+    ) external;
+
+    function rejectResource(
+        uint256 tokenId,
+        uint256 index,
+        uint64 resourceId
+    ) external;
+
+    function rejectAllResources(uint256 tokenId, uint256 maxRejections)
+        external;
+
+    function setPriority(uint256 tokenId, uint16[] calldata priorities)
+        external;
+
+    function getActiveResources(uint256 tokenId)
+        external
+        view
+        returns (uint64[] memory);
+
+    function getPendingResources(uint256 tokenId)
+        external
+        view
+        returns (uint64[] memory);
+
+    function getActiveResourcePriorities(uint256 tokenId)
+        external
+        view
+        returns (uint16[] memory);
+
+    function getResourceOverwrites(uint256 tokenId, uint64 newResourceId)
+        external
+        view
+        returns (uint64);
+
+    function getResourceMetadata(uint256 tokenId, uint64 resourceId)
+        external
+        view
+        returns (string memory);
+
+    // Approvals
+    function approveForResources(address to, uint256 tokenId) external;
+
+    function getApprovedForResources(uint256 tokenId)
+        external
+        view
+        returns (address);
+
+    function setApprovalForAllForResources(address operator, bool approved)
+        external;
+
+    function isApprovedForAllForResources(address owner, address operator)
+        external
+        view
+        returns (bool);
+}