feat: add vgv-bump-version skill

Description

Proposal to add a vgv-bump-version skill to the plugin that automates the Flutter app version bump workflow — from computing the new version to committing the change on a dedicated release branch.

What it does

The skill updates the version field in pubspec.yaml and commits the change on a dedicated release branch. It accepts an optional explicit version (e.g. 5.21.0); when omitted, it analyzes recent git commits and proposes a version following Semantic Versioning 2.0.0

The skill presents its reasoning and the proposed version to the user for confirmation before making any changes.

Workflow

1. Read current version: MAJOR.MINOR.PATCH+BUILD from pubspec.yaml
2. Compute new version (explicit argument or SemVer analysis of commits since last tag)
3. Update pubspec.yaml
4. Confirm with user before proceeding
5. Create branch chore/Release-preparation-X.Y.Z
6. Commit: chore(version): bump version to X.Y.Z+BUILD

Usage

/vgv-bump-version           # auto-proposes version from commits
/vgv-bump-version 5.21.0    # explicit version

Requirements

• All CI/CD checks are passing.
• There is no drop in the test coverage percentage.

Additional Context

No response

Start by inspecting the plugin's existing skill structure, then use pubspec.yaml and recent git commits or tags to trace the version-bump workflow. Done means the skill supports an explicit or proposed SemVer version, asks for confirmation, updates pubspec.yaml, creates the specified release branch, and commits the change with the required message.