feat(meta): document sudo_users_sudoers via argument specs

The only variable of the role was documented in defaults/main.yaml comments alone. An argument spec makes the variable
discoverable through ansible-doc and lets ansible reject a wrong type early.

The entries are intentionally left without suboptions. Argument spec validation fills missing suboptions with none,
which would turn the item.user | default('') | length conditions in tasks/main.yaml into a runtime error.

Co-authored-by: Copilot <copilot@github.com>

meta/argument_specs.yaml

@@ -0,0 +1,17 @@
+---
+argument_specs:
+  main:
+    short_description: "Role to configure sudoers on different distributions"
+    description:
+    - "This Ansible role installs sudo and manages drop-in files in /etc/sudoers.d."
+    - "Each drop-in file grants a unix user or a unix group the permission to execute commands, optionally as another
+      unix user."
+    author: "Markus Pesch"
+    options:
+      sudo_users_sudoers:
+        description:
+        - "List of sudoers drop-in files. Each entry must define either 'user' or 'group', but not both."
+        - "Supported keys are 'commands', 'filename', 'group', 'nopassword', 'runas', 'state' and 'user'."
+        type: list
+        elements: dict
+        default: []