Format all *.go files to have the empty line above the package declaration

[ckadner]

We should be consistently format all *.go files to have an empty line above the package declaration.

Without the empty line, go fmt will treat the license header as the package doc and reformat it according to Go doc format standards, and IDE will show the license text as package documentation 🙃

Originally posted by @ckadner in #68 (comment)

[spolti]

The goal is to add a new step to take care of the license headers as part of the go fmt make goal to keep it consistent across all files it is present.

This new step will have:

• a standalone make goal: make add-header
• will be called as part of the make fmt

Pre requisites:

• the headers should not have tabs, only spaces.

Tool to use:

• go install github.com/google/addlicense@latest

Makefile call:

.PHONY: addheaders
addheaders:
	./scripts/addheaders.sh