Add programmatic API to fold and unfold all code regions

[jpdup]

Currently, CodeCrafterController supports code folding through callbacks like setFoldAtCallback, but there is no public API to programmatically trigger folding or unfolding of all foldable regions.

This limitation makes it difficult to:

• Implement "Collapse All" / "Expand All" buttons in an IDE-style UI.
• Restore user fold states after reopening a file.
• Provide shortcuts or automated folding behavior.

—
Feature Request
Please add public methods (or similar) to CodeCrafterController, e.g.:
dart
controller.collapseAll();
controller.expandAll();
controller.toggleFoldAtLine(int lineIndex);

Or a method such as setFoldStateForAll(bool folded).
These should update internal folding state and call refresh() to re-render.

Motivation / Use Case
I’m building a custom Flutter code editor and need UI buttons or keyboard shortcuts for “Collapse All / Expand All.”

Current Workaround
Limitation: only workaround is to redefine foldAt callback and call controller.refresh(), which isn’t ergonomic for UI actions.

—
Suggested Implementation
• Add collapseAll()

[heckmon]

You can programmatically fold any foldable lines using controller.foldAt(line_numer).
However I cannot update anything right now because I'm too busy with my college exams.

Also I'm building a new code editor called flutter_code_forge from scratch using RenderBox by drawing pixels in canvas instead of extending TextEditingController. It's a complete alternative to this package . Because Flutter's built in TextField lags for large text files with 2000+ lines of code.
So I will add these features in flutter_code_forge.

[heckmon]

@jpdup Hello, finally, I published the new package code_forge with features like foldAll, unfoldAll, toggleFold, etc.
Have a look: https://pub.dev/packages/code_forge