Split long lines only available behind environment string

[sevein]

Hi @mvdan, thanks for maintaning this project. I've noticed that golangci-lint is unable to use gofumpt's feature to split long lines because it's only accessible with the environment string GOFUMPT_SPLIT_LONG_LINES=on which is not something that can be actioned via golangci-lint.

Would you be open to considering adding a new option or incorporating it into the extra rules?

Thank you in advance!

Related: golangci/golangci-lint#4253