Add skill-image-gen plugin: AI image generation with OpenAI and Gemini (#1696)

Adds a skill that lets users generate images (icons, sprites, textures,
mockups) directly from their coding workflow using OpenAI gpt-image-2 or
Google Gemini. BYO API key — the skill guides users through setup on
first use.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

plugins/skill-image-gen/.github/plugin/plugin.json

@@ -0,0 +1,25 @@
+{
+  "name": "skill-image-gen",
+  "description": "Generate images using AI directly from your coding workflow. Supports OpenAI (gpt-image-2) and Google Gemini. BYO API key — the skill guides you through setup on first use.",
+  "version": "1.0.0",
+  "keywords": [
+    "image-generation",
+    "openai",
+    "gemini",
+    "ai",
+    "art",
+    "sprites",
+    "textures",
+    "icons"
+  ],
+  "author": {
+    "name": "adamd9",
+    "url": "https://github.com/adamd9"
+  },
+  "homepage": "https://github.com/adamd9/skill-image-gen",
+  "repository": "https://github.com/github/awesome-copilot",
+  "license": "MIT",
+  "skills": [
+    "./skills/generate-image/"
+  ]
+}