Fixed reactivity of colors prop for rate component

[lukaszb]

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What I wanted is to allow user to rate some items and also see other users's average rating. Until user rates the item herself that average rating should be "muted" (dimmed colors), so I wanted to pass colors prop. However, I then noticed that changing that colors array at parent component have no impact on the colors at rate component. Looking at the code I can see that colorMap is prepared once at the created hook. This makes colors prop non-reactive which is odd.

I've made colorMap a computed value that should be based on colors prop.