Add niri-animations plugin (#223)

Animation preset picker for niri: choose a .kdl preset, set the global
slowdown factor, or turn animations off. Ships a floating and a
bar-attached panel plus a control-center tile.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

niri-animations/translations/en.json

@@ -0,0 +1,34 @@
+{
+  "title": "Niri Animations",
+  "preset": "Preset",
+  "no_preset": "No preset (base pack)",
+  "animations_on": "Animations on",
+  "animations_off": "Animations off",
+  "random": "Random",
+  "speed": "Speed",
+  "speed_hint": "above 1 is slower",
+  "shortcut_label": "Animations",
+  "status_presets_found": "presets in",
+  "status_base_pack": "Base pack",
+  "status_off": "Animations disabled.",
+  "status_read_error": "Could not read",
+  "status_write_error": "Could not write",
+  "settings": {
+    "presets_dir": {
+      "label": "Presets directory",
+      "description": "Folder scanned for .kdl animation presets"
+    },
+    "target_file": {
+      "label": "Target file",
+      "description": "File rewritten with the chosen preset and speed. Your niri config must include it after the base animations."
+    },
+    "include_prefix": {
+      "label": "Include prefix",
+      "description": "Path prefix written in the include line, relative to the target file"
+    },
+    "reload_command": {
+      "label": "Reload command",
+      "description": "Run after writing, so the compositor picks up the change"
+    }
+  }
+}