feat: support ESM plugins or plugins with named exports

[calfzhou]

check list

• Add test cases for the changes.
• Passed the CI test.

Description

This PR adds support for loading plugins that use ESM-style exports (interop) or named exports.

Previously, the renderer assumed that require('plugin-name') would directly return the plugin function. However, some modern plugins or dual-mode packages might export the plugin function under a default property or a specific named export.

With this change, users can now specify an import property in the plugin configuration to choose which export to use.

Logic:

• If the required module is an object and the user specifies an import key (or defaults to 'default'), it tries to use that property.
• If the property doesn't exist, it throws a descriptive error listing available exports.
• Fallback behavior is preserved for standard CommonJS plugins.

Example Config:

plugins:
  - name: 'some-esm-plugin'
    import: 'default' # Optional, defaults to 'default' if the module is an object
    options: ...

Additional information

• Updated README.md with usage examples for the new feature.
• Added unit tests covering default and named exports.