misc: added flake template (#219)

* Added simple flake template

* Added readme to template

* Updated readme to show how to use the template

* Formatting

* removed unused file from template

* Fixed template url and pkgs

* Formatting

lib/check.nix

@@ -0,0 +1,30 @@
+{pkgs, ...}: {
+  checkNvim = {
+    name,
+    nvim,
+    ...
+  }:
+    pkgs.stdenv.mkDerivation {
+      name = name;
+
+      nativeBuildInputs = [nvim];
+
+      dontUnpack = true;
+      # We need to set HOME because neovim will try to create some files
+      #
+      # Because neovim does not return an exitcode when quitting we need to check if there are
+      # errors on stderr
+      buildPhase = ''
+        output=$(HOME=$(realpath .) nvim -mn --headless "+q" 2>&1 >/dev/null)
+        if [[ -n $output ]]; then
+        	echo "ERROR: $output"
+          exit 1
+        fi
+      '';
+
+      # If we don't do this nix is not happy
+      installPhase = ''
+        mkdir $out
+      '';
+    };
+}