feat: add vgv-bump-version skill

[alvaroarmijos]

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