feat: allow multiple plugins to be registered at once

[nperez0111]

Changes Overview

This allows for editor.registerPlugin to take either a single plugin (original behavior) or an array of plugins as it's argument.

Implementation Approach

Testing Done

Verification Steps

Additional Notes

Checklist

• I have created a changeset for this PR if necessary.
• My changes do not break the library.
• I have added tests where applicable.
• I have followed the project guidelines.
• I have fixed any lint issues.

Related Issues

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[Copilot]

Pull Request Overview

This PR enhances the registerPlugin method to accept either a single plugin or an array of plugins, improving the API's flexibility for batch plugin registration.

• Modified the registerPlugin method signature to accept generic type T extends Plugin | Plugin[]
• Updated the method parameters and implementation to handle both single plugins and plugin arrays
• Added array spreading logic to flatten plugin arrays when merging with existing plugins

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[Copilot]

The handlePlugins callback parameter type may be confusing when T is Plugin[]. Consider using a more explicit type like (newPlugin: Plugin | Plugin[], plugins: Plugin[]) => Plugin[] to clarify that the callback receives the same input type as the method parameter.

Suggested change

	public registerPlugin<T extends Plugin | Plugin[]>(
	plugin: T,
	handlePlugins?: (newPlugin: T, plugins: Plugin[]) => Plugin[],
	public registerPlugin(
	plugin: Plugin | Plugin[],
	handlePlugins?: (newPlugin: Plugin | Plugin[], plugins: Plugin[]) => Plugin[],