feat: resolve did:plc

[fforbeck]

DID PLC Resolver

Overview

Created a DID resolver helper to support both Web and PLC DID resolution. The resolver uses an optional options object and has dedicated resolution functions for each DID method that can be easily extended.

Main Changes

• Refactored createDidResolver to use optional options object
• Added separate resolveDIDWeb and resolveDIDPlc functions
• Added proper parsing of PLC verification methods using multikey format

Usage

const resolver = createDidResolver({
  principalMapping, // optional mapping of Web DIDs to DID keys
  plcClient        // optional PLC client for PLC DID resolution
})

// Can also be called with no options
const resolver = createDidResolver()

Related: storacha/project-tracking#463