Add BackgroundColorTo Unit Tests

[TheCodeTraveler]

Description

Adds Unit Tests for #88

Detailed Solution

• Adds ColorAnimationExtensions_Test.cs
• Adds AnimationExtensions.cs
  • Introduces EnableAnimations extension method for IView
    • e.g. myLabel.EnableAnimations()
    • Allows us to set IMauiContext on an IView that can handle animations, which is required by Microsoft.Maui.Controls.AnimationExtensions.Animate
    • Otherwise, Animation.Commit will throw ArgumentException, causing BackgroundColorTo to return false
• Add abstract keyword to BaseTest.cs

[bijington]

Looking great!