HF-7: Move out sops config

* Updated configuration.nix to match latest homefree
* Added secrets config
* Updated Readme

secrets/README.md

@@ -0,0 +1,22 @@
+Secrets config
+--------------
+
+1. Generate appropriate GPG keys. You will need a private SSH key at ~/.ssh/id_rsa
+
+```
+./generate-gpg-keys.sh
+```
+
+Create secrets file in this folder. Use the following commands:
+
+```
+sops authentik.yaml
+sops backup.yaml
+sops ddclient.yaml
+sops linkwarden.yaml
+sops nextcloud.yaml
+sops tailscale.yaml
+```
+
+And copy the contents from the appropriate file in the `secrets-unencrypted` folder, changing
+the values as required.