Feature/add trailing comma

[BlakeNeko]

Details in #53 .

[newtextdoc1111]

About Unit Test Failures

The existing unit tests are now failing because the auto-formatter removes trailing commas. This is due to the test code not being updated to accommodate the new behavior.
I will fix the unit test code on my end after merging this PR into the dev branch.

As a side note, you can run the unit tests locally with npm test command. However, please note that it has currently only been confirmed to work on Ubuntu running on WSL2 and in GitHub Actions 😵
Running unit tests on Windows results in errors, which is something I'd like to resolve in the future.

PS: I will also update the JP translation files on my end after merging into the dev branch!