NextJS Template Upgrades

There are a few upgrades we can make to this template to provide additional value over just creating a new NextJS project via npm.

* Add a .github directory that has workflows for linting, and running tests, blocking merges on failure
* Add content security policy protections

_Originally posted by @mattrandallbecker in https://github.com/abcxyz/abc/pull/209#pullrequestreview-1627305712_