Serialize the next numeric name

[jeremyroman]

We need to explicitly convert this from an integer to a string.

Fixes #208.

• [x] At least two implementers are interested (and none opposed):
  • Google Chrome
  • n/a (change is simply fixing a bug in a non-controversial way, per this comment)
• [x] Tests are written and can be reviewed and commented upon at:
  • n/a (this is a fix to how the spec expresses this, but does not represent a behavior change, and existing tests cover this behavior)
• [x] Implementation bugs are filed:
  • Chromium: n/a (believed to work correctly in Chromium)
  • Gecko: https://bugzilla.mozilla.org/show_bug.cgi?id=1731418 (vendor does not yet implement the spec)
  • WebKit: [no known URLPattern bug] (vendor does not yet implement the spec)
  • Deno: n/a (no reason to believe a change is required)
  • kenchris/urlpattern-polyfill: n/a (no reason to believe a change is required)
• [x] MDN issue is filed: n/a (change is on a spec detail not expressly documented)
• [x] The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

---

:boom: Error: 400 Bad Request :boom:

PR Preview failed to build. (Last tried on Jan 26, 2024, 10:06 PM UTC).

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