Make PluginGroup.add and PluginGroup.remove chainable

[waynemwashuma]

Objective

Improve the PluginGroup API by enabling method chaining.

Solution

Previously, PluginGroup#add() and PluginGroup#remove() mutated internal state but returned void.

This prevented fluent configuration patterns such as:

group.add(pluginA).add(pluginB)

Why this approach

Improves ergonomics for plugin composition

Showcase

Before

const group = new PluginGroup()

group.add(pluginA)
group.add(pluginB)
group.remove(typeid(MyPlugin))

After

const group = new PluginGroup()
  .add(pluginA)
  .add(pluginB)
  .remove(typeid(MyPlugin))

Migration guide

No migration required.

Checklist

• I have updated the documentation accordingly.
• I have added tests to cover my changes.