micro: add module

This adds initial bare-bones support for the `micro` editor.

modules/programs/micro.nix

@@ -0,0 +1,43 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.programs.micro;
+
+  jsonFormat = pkgs.formats.json { };
+
+in {
+  meta.maintainers = [ hm.maintainers.mforster ];
+
+  options = {
+    programs.micro = {
+      enable = mkEnableOption "micro, a terminal-based text editor";
+
+      settings = mkOption {
+        type = jsonFormat.type;
+        default = { };
+        example = literalExpression ''
+          {
+            autosu = false;
+            cursorline = false;
+          }
+        '';
+        description = ''
+          Configuration written to
+          <filename>$XDG_CONFIG_HOME/micro/settings.json</filename>. See
+          <link xlink:href="https://github.com/zyedidia/micro/blob/master/runtime/help/options.md"/>
+          for supported values.
+        '';
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    home.packages = [ pkgs.micro ];
+
+    xdg.configFile."micro/settings.json".source =
+      jsonFormat.generate "micro-settings" cfg.settings;
+  };
+}