Update github workflow to automate version/links

[jalensailin]

The github workflow file has been updated to automate changing some of the values in system.json: version, manifest, and download. All we have to do is tag a release of the form vX.Y.Z and these values will automatically be updated with the correct links on build. In addition, the system.json file will be attached to the release along with the deltagreen.zip. This will make it really easy for someone to install a specific version of the system via manifest link alone, and it leaves less room for error on our part (i.e. we only have to write the correct version once, when making the tag.

This update also prevents development files/folders from being included in the .zip

To test:

Note, this is kind of hard to test without merging first, since github will only recognize the action if its in the master branch. I'd review the few code changes and as long as you see no glaring mistakes, we can merge this, and then you/I can test everything.

1. Cut a release and assign a new tag vTest or something similar (start with a lower case v).
2. Let the build system do its thing.
3. Once build system has completed, check that the release has a system.json and a deltagreen.zip attached.
4. Ensure that the download and manifest fields in system.json do not point to dead links.
5. Ensure that the version field in system.json reads Test (or whatever you named the tag, without the v).
6. Download the deltagreen.zip file and ensure that the system.json in there looks the same.
7. Ensure no development files such as package.json, package-lock.json, or any folder/file starting with a . is included in the .zip