✨ Add Highfivve as AMP RTC vendor

[muuki88]

This pull requests adds AMP RTC vendor Highfivve to the list of AMP RTC vendors.

Example integration

<amp-ad
  width="320"
  height="50"
  type="network-foo"
  data-slot="/1234/5678"
  rtc-config='{
    "vendors": {
      "highfivve": {"TAG_ID": "1", "ACCOUNT_ID":"my-account"}
      },
    "timeoutMillis": 750}'
>
</amp-ad>

Follow up of the mess I created in #33203 . Sorry for the inconvenience 🙇‍♂️

[calebcordry]

Sorry we have some flaky tests, could you try rebase or merging latest master. It should fix the tests. Let me know if you run into problems.

[muuki88]

Looks fine now ❤️

When this gets merged, how long will it take to be available on AMP pages?

[calebcordry]

Thanks for contributing! You can test using nightly tomorrow. It will hit beta next week, then prod the following week. You can find more details at https://amp.dev/documentation/guides-and-tutorials/learn/spec/release-schedule/

[muuki88]

Thanks for your help ❤️