krebs: move github modules to subdir

krebs/3modules/default.nix

@@ -25,8 +25,7 @@ let
       ./exim.nix
       ./fetchWallpaper.nix
       ./git.nix
-      ./github-hosts-sync.nix
+      ./github
-      ./github-known-hosts.nix
       ./go.nix
       ./hidden-ssh.nix
       ./hosts.nix

krebs/3modules/github/default.nix

@@ -0,0 +1,6 @@
+{
+  imports = [
+    ./hosts-sync.nix
+    ./known-hosts.nix
+  ];
+}