Install emacs.nix

- To avoid having to configure emacs I'll be using spacemacs
- Emacs is now only used for my EPQ. I'm probably going to be disabling it later
- As spacemacs needs to write its configuration during the setup, I'll have to
  do it imperatively
diff --git a/config.nix b/config.nix
new file mode 100644
index 0000000..3eeeca0
--- /dev/null
+++ b/config.nix
@@ -0,0 +1,3 @@
+{
+  emacs.enable = true;
+}