Add README documentation (docs)

README.md

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+# template-stacks
+
+This repository is a template of a monorepo for declaratively managing infrastructure and configuration.
+
+## Updating from the template
+
+To pull updates from this template to your repository instance, add this template repository as a remote to your
+repository instance:
+
+```bash
+git remote add template [email protected]:cncsc/template-stacks.git
+```
+
+Then, fetch the most recent changes:
+
+```bash
+git fetch --all
+```
+
+Then, merge the changes from this template to your repository instance:
+
+```bash
+git merge template/main --allow-unrelated-histories
+```