No template for new PRs

[FroggyFlox]

Although one can find detailed documentation on how to submit a PR for a new or updated rock-on in the README.md file, it remains unclear for a contributor what the guidelines for formatting the JSON file are, or what information should be included.

Although this can be partially automated (see #91), one could use Github PR templates to help the contributor prepare the best PR submission possible. This would help alleviate the work required in common edits prior to PR merge and thus greatly accelerate the successful PR process.

One could thus provide a checklist for the contributor to:

1. provide the contributor with additional pointers to make sure the included docker image(s) fit general guidelines (when appropriate)
2. ensure the JSON file was verified to be valid
3. ensure the required information is provided with pointers on where it should be. For instance, is the link to the docker hub image included in the "description" object?
4. ensure an entry was added to the root.json file (when applicable)

One could also add template to make sure the information required by reviewer(s) is provided:

5. project name and link to project
6. image used with link to docker hub
7. benefits of this rock-on to the Rockstor community: improvement(s) on existing rock-on, addresses a current need, "better" image used, etc...

The list above is of course only a suggestion and can easily be improved as needed.