FleatherField cursor does not stay visible when focused

[kane-knowby]

When the cursor moves outside of the view (or behind the keyboard), the parent scrollable should scroll so that the cursor stays in view, the same way that TextFormField does.

Steps to Reproduce

• Add a FleatherField to a ListView, with plenty of empty space above and below the field to scroll.
• Type in the FleatherField until the cursor disappears beneath the keyboard

Environment

• OS: iOS/Web/Android
• Flutter version: 3.24
• Fleather version: 1.18.0