fix: add jest-util as an extra dependency of ts-jest (#611)

For some reason `ts-jest` is now listing `jest-util` as an optional peer
dependency even though it seems to be always required, and Yarn Berry
doesn't like that 🤷

Author: G-Rath

variants/frontend-stimulus-typescript/template.rb

@@ -3,6 +3,7 @@
 add_yarn_package_extension_dependency("@testing-library/jest-dom", "@types/aria-query")
 add_yarn_package_extension_dependency("ts-jest", "@jest/transform")
 add_yarn_package_extension_dependency("ts-jest", "@jest/types")
+add_yarn_package_extension_dependency("ts-jest", "jest-util")
 add_yarn_package_extension_dependency("@jest/test-result", "jest-haste-map")
 add_yarn_package_extension_dependency("@jest/test-result", "jest-resolve")
 add_yarn_package_extension_dependency("jest-cli", "@types/yargs")