Bump babylonjs-materials from 5.54.0 to 6.20.0

Bumps [babylonjs-materials](https://github.com/BabylonJS/Babylon.js) from 5.54.0 to 6.20.0.
- [Release notes](https://github.com/BabylonJS/Babylon.js/releases)
- [Changelog](https://github.com/BabylonJS/Babylon.js/blob/master/CHANGELOG.md)
- [Commits](BabylonJS/Babylon.js@5.54.0...6.20.0)

---
updated-dependencies:
- dependency-name: babylonjs-materials
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -463,7 +463,7 @@
         "@vscode/webview-ui-toolkit": "^1.2.2",
         "assert": "^2.0.0",
         "babylonjs": "^5.54.0",
-        "babylonjs-materials": "^5.54.0",
+        "babylonjs-materials": "^6.20.0",
         "buffer": "^6.0.3",
         "console-browserify": "^1.2.0",
         "constants-browserify": "^1.0.0",