Add lintr for automated PR reviews

[Bisaloo]

No description provided.

[sbfnk]

This looks great. How do you feel about a linter for max 80 characters per line? I tend to try and stick with it (if not consistently in this package) but perhaps it's not needed.

[sbfnk]

Looking over the code, the another good linter might be for snake_case variable names.

[Bisaloo]

Yes, feel free to re-enable object_name_linter and line_length_linter. I didn't do it here because it requires too many changes in the existing code.

If you want to fix the current code and re-enable these linters, I would recommend you start by re-enabling the relevant linter, then run lintr::lint_package() and you should get a list of all the lines to fix.

Also note that line_length_linter can be configured to another value than 80 characters.