micro: add module

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

tests/modules/programs/micro/default.nix

@@ -0,0 +1 @@
+{ micro = ./micro.nix; }

tests/modules/programs/micro/micro.nix

@@ -0,0 +1,24 @@
+{ ... }:
+
+{
+  programs.micro = {
+    enable = true;
+
+    settings = {
+      autosu = false;
+      cursorline = false;
+    };
+  };
+
+  test.stubs.micro = { };
+
+  nmt.script = ''
+    assertFileContent home-files/.config/micro/settings.json \
+    ${builtins.toFile "micro-expected-settings.json" ''
+      {
+        "autosu": false,
+        "cursorline": false
+      }
+    ''}
+  '';
+}