StyleGuide - In Change Detection, "Use OnPush..."

[mgechev]

To be discussed.

// cc @wardbell @johnpapa

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• Use OnPush change detection strategy for pure/dumb components that accepts as input immutable data.

  Why?: Angular will optimize the performance of your application dramatically by not performing change detection over the entire sub tree with root the given pure component.

[johnpapa]

We need one like this, but it needs more why, more avoid code and more recommendation code.