Add visual-pr plugin — screenshot capture, annotation, and PR embedding (#1804)

* Add visual-pr plugin: screenshot capture, annotation, PR embedding, and screen recording

Four skills that teach Copilot to capture UI screenshots (Playwright + PIL),
annotate them with algorithmic label placement, embed before/after images
in PR descriptions, and record animated GIF demos.

Includes demo images showing the annotation engine on GitHub Issues.

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

* Update generated README tables and marketplace.json

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

* Embed annotate.py module in image-annotations skill

The full working module (annotate_image, grid_image, diff_images) is now
included as a code block so users can save it as annotate.py and import
directly. Scrubbed project-specific labels from examples.

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

* Address review feedback: mss.mss() context manager, fix RECT struct, consistent placeholder

- Use mss.mss() context manager instead of mss.MSS() (ui-screenshots, screen-recording)
- Fix broken RECT struct in window+GIF combining example (screen-recording)
- Consistent projectId placeholder in AzDO upload example (pr-screenshots)

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

---------

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

plugins/visual-pr/.github/plugin/plugin.json

@@ -0,0 +1,24 @@
+{
+  "name": "visual-pr",
+  "description": "Capture, annotate, and embed screenshots and animated GIF demos in pull request descriptions. Includes Playwright-based UI capture, PIL image annotations, PR embedding workflows for GitHub and Azure DevOps, and screen recording with variable timing.",
+  "version": "1.0.0",
+  "keywords": [
+    "screenshots",
+    "pull-request",
+    "before-after",
+    "annotations",
+    "playwright",
+    "gif",
+    "screen-recording",
+    "visual"
+  ],
+  "author": { "name": "Awesome Copilot Community" },
+  "repository": "https://github.com/github/awesome-copilot",
+  "license": "MIT",
+  "skills": [
+    "./skills/image-annotations/",
+    "./skills/pr-screenshots/",
+    "./skills/screen-recording/",
+    "./skills/ui-screenshots/"
+  ]
+}