Add Document-Isolation-Policy (#1673)

Close #1672, 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://wicg.github.io/document-isolation-policy/",
  "seriesComposition": "full",
  "shortname": "document-isolation-policy",
  "series": {
    "shortname": "document-isolation-policy",
    "currentSpecification": "document-isolation-policy",
    "title": "Document-Isolation-Policy",
    "shortTitle": "Document-Isolation-Policy",
    "nightlyUrl": "https://wicg.github.io/document-isolation-policy/"
  },
  "organization": "W3C",
  "groups": [
    {
      "name": "Web Platform Incubator Community Group",
      "url": "https://www.w3.org/community/wicg/"
    }
  ],
  "nightly": {
    "url": "https://wicg.github.io/document-isolation-policy/",
    "status": "Draft Community Group Report",
    "alternateUrls": [],
    "repository": "https://github.com/WICG/document-isolation-policy",
    "sourcePath": "index.bs",
    "filename": "index.html"
  },
  "title": "Document-Isolation-Policy",
  "source": "spec",
  "shortTitle": "Document-Isolation-Policy",
  "categories": [
    "browser"
  ],
  "standing": "good"
}
```
</details>

### Tests
These changes look good! 😎

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

specs.json

@@ -686,6 +686,7 @@
     "url": "https://wicg.github.io/direct-sockets/",
     "standing": "pending"
   },
+  "https://wicg.github.io/document-isolation-policy/",
   "https://wicg.github.io/document-picture-in-picture/",
   "https://wicg.github.io/document-policy/",
   "https://wicg.github.io/entries-api/",

src/data/monitor.json

@@ -405,10 +405,6 @@
     "https://dev.w3.org/html5/html-sourcing-inband-tracks/": {
       "lastreviewed": "2025-01-01",
       "comment": "no longer worked on and implementation status is unclear"
-    },
-    "https://wicg.github.io/document-isolation-policy/": {
-      "comment": "Chrome status entry https://chromestatus.com/feature/5141940204208128 says no active development and no known standard positions yet",
-      "lastreviewed": "2025-01-01"
     }
   }
 }