chore: relicense to Apache-2.0

This commit relicenses all of the codebase to Apache-2.0. The logic
behind this is that so much of the codebase is Apache-2.0, from
before the fork, that it doesn't make sense to dual-license the
repository. All projects under this org going forward will be GPL,
but stencil itself will stay as Apache-2.0

For proof of authors who contributed during this time's agreement
to relicense, see the PR associated with this change.

.goreleaser.yaml

@@ -58,7 +58,7 @@ brews:
       name: GitHub Actions
       email: 41898282+github-actions[bot]@users.noreply.github.com
     homepage: https://stencil.rgst.io
-    license: AGPL-3.0
+    license: Apache-2.0
     description: "A modern living-template engine for evolving repositories"
     dependencies:
       - name: git