Add Open Screen Network Protocol (#1603)

Close #1600, 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://www.w3.org/TR/openscreen-network/",
  "seriesComposition": "full",
  "shortname": "openscreen-network",
  "series": {
    "shortname": "openscreen-network",
    "currentSpecification": "openscreen-network",
    "title": "Open Screen Network Protocol",
    "shortTitle": "Open Screen Network Protocol",
    "releaseUrl": "https://www.w3.org/TR/openscreen-network/",
    "nightlyUrl": "https://w3c.github.io/openscreenprotocol/network.html"
  },
  "organization": "W3C",
  "groups": [
    {
      "name": "Second Screen Working Group",
      "url": "https://www.w3.org/2014/secondscreen/"
    }
  ],
  "release": {
    "url": "https://www.w3.org/TR/openscreen-network/",
    "status": "First Public Working Draft",
    "filename": "Overview.html"
  },
  "nightly": {
    "url": "https://w3c.github.io/openscreenprotocol/network.html",
    "status": "Editor's Draft",
    "alternateUrls": [],
    "repository": "https://github.com/w3c/openscreenprotocol",
    "sourcePath": "network.bs",
    "filename": "network.html"
  },
  "title": "Open Screen Network Protocol",
  "source": "w3c",
  "shortTitle": "Open Screen Network Protocol",
  "categories": [
    "browser"
  ],
  "standing": "good"
}
```
</details>

### Tests
These changes look good! 😎

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

specs.json

@@ -1471,6 +1471,7 @@
   "https://www.w3.org/TR/navigation-timing-2/",
   "https://www.w3.org/TR/network-error-logging/",
   "https://www.w3.org/TR/openscreen-application/",
+  "https://www.w3.org/TR/openscreen-network/",
   "https://www.w3.org/TR/openscreenprotocol/",
   "https://www.w3.org/TR/orientation-event/",
   "https://www.w3.org/TR/orientation-sensor/",