Streamline & publish process for contributing to QuickPost

[aurooba]

Right now there are a few issues with QuickPost's processes. It was developed quickly and set up as a repository that would only ever have one person contributing to it. While that's likely to remain the case for now, it would be good to have a process that welcomes and eases the ability for folks to contribute if they wish.

To that end, I propose the following adjustments:

1. Creating a new develop branch which becomes the source of truth for new features and development that haven't been officially released yet. This way the main branch is always the current published version of the plugin.
2. Creating a CONTRIBUTING.md doc that details how one can go about contributing to the plugin if they so wish.

[aurooba]

Develop branch has now been set to default. Next step is to create a contributing doc.

[kkoppenhaver]

Some important pieces of info that should be included:

• Does the plugin use any sort of coding standard, linter, or any automated tooling that has to pass before a review on the PR should be requested?
• What (if any) is the convention for naming branches that are going to turn into pull requests? (it looks like from the branches you've made yourself, you already sort of have an add/* or fix/* convention established).

Might also make sense to take a look at one of the GitHub examples.

Going to take a pass at a PR and these are just the things that I thought of while I was going through the process. Hope it's helpful!