Formatting of package.json is not preserved

When using this plugin to automatically bump the `package.json` version it completely rewrites the file if it wasn't already indented with 4 spaces. This is probably unwanted behavior, because it leads to [extra changes in the diff of release commits](https://github.com/sanderploegsma/jupyterlab_remote_url/commit/f34c867978222c4460da738597d210d688321db0#diff-7ae45ad102eab3b6d7e7896acd08c427a9b25b346470d7bc6507b6481575d519). Additionally, it caused the linting stage of my repository to fail because the `package.json` was incorrectly formatted after it was updated by an automated release pipeline.

Instead, it would be much better if this plugin only changes the line in the `package.json` containing the actual version, and leave the rest of the file untouched.