build(deps-dev): bump @fortawesome/free-solid-svg-icons

Bumps [@fortawesome/free-solid-svg-icons](https://github.com/FortAwesome/Font-Awesome) from 5.15.4 to 6.4.2.
- [Release notes](https://github.com/FortAwesome/Font-Awesome/releases)
- [Changelog](https://github.com/FortAwesome/Font-Awesome/blob/6.x/CHANGELOG.md)
- [Commits](FortAwesome/Font-Awesome@5.15.4...6.4.2)

---
updated-dependencies:
- dependency-name: "@fortawesome/free-solid-svg-icons"
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

package.json

@@ -11,7 +11,7 @@
         "@creativebulma/bulma-tooltip": "^1.2.0",
         "@fortawesome/fontawesome-svg-core": "^6.4.2",
         "@fortawesome/free-brands-svg-icons": "^6.4.2",
-        "@fortawesome/free-solid-svg-icons": "^5.15.4",
+        "@fortawesome/free-solid-svg-icons": "^6.4.2",
         "bulma": "^0.9.4",
         "katex": "^0.16.8",
         "psi": "^4.1.0",