feat: allow changing transition duration

[adil192]

Allows developers to specify the transition duration like so:

Navigator.of(context).push(
  NesVerticalCloseTransition.route<void>(
    pageBuilder: widget.openBuilder,
    duration: const Duration(milliseconds: 300),
  ),
);

Status

Ready for review

Description

Adds an optional argument to NesVerticalCloseTransition.route (and likewise with the other transition classes) to specify the transition duration, see adil192/ricochlime#41.

My first thought was to add a field to NesOverlayTransitionTheme but since the durations are different for each transition (i.e. 750ms vs 1750ms), it would be less verbose to just add a parameter to the ....route<T>() functions.

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore
• 🧪 Tests

[erickzanardo]

Thanks for the contribution! LGTM