New Lint: check_filesize

Thanks for the help to https://stackoverflow.com/questions/42884196/bash-check-if-input-is-empty-in-pipe

Large files cause various problems
- can't be displayed in GitLab
- thus can't be edited or read there (accessibility)
- slow down recipemd on CLI
- slow down recipemd on CI
- also applies to recipemd-find worsening the whole usage
- slows down IDEA on my computer (yes...)

And to let actions speak louder than my complains the CI now enforces a
max file limit of 1 MB. Basically every file is way wayyyy smaller than
1 MB except when it's one of the troublesome files which easily exceed
them.