* all: run gofumpt
https://github.com/mvdan/gofumpt
The main appeal for me here is that my (and many other peoples')
editors run this on save, so doing a single diff here
keeps other diffs minimal.
* .github/workflows: add gofumpt checker
* Add PipeCreateErrorCallback to handle pipe creation errors
* Add test for FailtobanPipeCreateFail
* Fix missing newline at end of file in pluginbase.go
