Update tool to use SVG

[darkwheel]

This pull request updates the package metadata and build process for the @darkwheel/pptb-solution-explorer project. The main changes include a version bump, improved icon handling, and enhancements to the build scripts.

Package metadata and build process improvements:

• Bumped the package version from 0.2.3 to 0.2.4 in package.json to reflect the latest changes.
• Added the icon field to package.json to specify the extension icon (icon/icon.svg).

Build script enhancements:

• Updated the build script to include a new copy-icon step, ensuring icons are copied to the distribution folder.
• Added a copy-icon script to copy the icon/ directory to dist/icon using shx.
• Introduced a finalize-package script to run npm shrinkwrap for locking dependencies.