Clean up some Dart lint recommendations?

[tyler-jewell]

I just forked this repo and want to say job well done. I really like the structure and want to contribute all I can. I am seeing quite a few Dart lint recommendations on my end. Would it be ok if I just submitted a PR correcting some of them?

I would say 80% of them are recommending lambda tear-offs which will make the code a lot cleaner:

Now:

After:

[github-actions]

👋 Thanks for reporting! @robrbecker will take a look.

[tyler-jewell]

I am not able to tie this to the PR I just created. Here's the link:

#345