Add Captured Surface Control (#1573)

Close #1568, adding the suggested spec to the list.

### Changes to `index.json`
This update would trigger the following changes in `index.json`:

<details><summary>Add spec (1)</summary>

```json
{
  "url": "https://w3c.github.io/mediacapture-surface-control/",
  "seriesComposition": "full",
  "shortname": "mediacapture-surface-control",
  "series": {
    "shortname": "mediacapture-surface-control",
    "currentSpecification": "mediacapture-surface-control",
    "title": "Captured Surface Control",
    "shortTitle": "Captured Surface Control",
    "nightlyUrl": "https://w3c.github.io/mediacapture-surface-control/"
  },
  "organization": "W3C",
  "groups": [
    {
      "name": "Web Real-Time Communications Working Group",
      "url": "https://www.w3.org/groups/wg/webrtc/"
    }
  ],
  "nightly": {
    "url": "https://w3c.github.io/mediacapture-surface-control/",
    "status": "Editor's Draft",
    "alternateUrls": [],
    "repository": "https://github.com/w3c/mediacapture-surface-control",
    "sourcePath": "index.html",
    "filename": "index.html"
  },
  "title": "Captured Surface Control",
  "source": "spec",
  "shortTitle": "Captured Surface Control",
  "categories": [
    "browser"
  ],
  "standing": "good"
}
```
</details>

### Tests
These changes look good! 😎

Co-authored-by: browser-specs-bot <>

specs.json

@@ -525,6 +525,7 @@
       "sourcePath": "actions/index.html"
     }
   },
+  "https://w3c.github.io/mediacapture-surface-control/",
   "https://w3c.github.io/permissions-registry/",
   {
     "url": "https://w3c.github.io/reporting/network-reporting.html",