Various updates (see below)

[nsotgui]

• Add first pass on quickbooks bill
• Add github actions for build and future tests
• Refactor project layout according to recommended standards: https://github.com/golang-standards/project-layout

[ghost]

Thanks for your effort. I'm going to merge this, but there are a few things we would hope to see done differently in future PRs:

• One issue per PR

• Use amend and rebase to polish commits before opening a PR. Commit messages like 'try fix' make sense for personal use, but they don't help us make sense of the changes. In general, if a commit only fixes a problem with a previous commmit, it should be merged into it using amend or the 'fixup' command in interactive rebase.

I'm also going to undo the change to the project directory structure, because it doesn't sound like that's really a standard and it breaks compatibility.

[nsotgui]

Make senses, I'll do it for future PR.

I don't have a strong opinion on the pkg folder but you raised a good question on the compatibility, how about we start versioning/releasing versions of this repo?