Add animation with an opacity on navigation bar

Description

Make navigation bar animate to a darker color while moving to the widget page, and reverse to original state while going back to home.

Screenshots

navbar-animation

Tests

• Swipe right on home screen carefully watching the navigation bar
• Color animates to a darker variant when scroll is finished and we are on widget page
• Going back to home makes the navigation bar animate back to the original color

Issues

e/backlog#5440 (comment 295987)

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