Add syncRedirectDomain for vercel.com template

[RhysSullivan]

Description

I should've read the Some common feedback part of the docs my bad. Was doing the implementation and realized I'd need syncRedirectDomain so this is updating the template to support that. Thanks for the quick review on the last one

Type of change

Please mark options that are relevant.

• New template
• Bug fix (non-breaking change which fixes an issue in the template)
• New feature (non-breaking change which adds functionality to the template)
• Breaking change (fix or feature that would cause existing template behavior to be not backward compatible)

How Has This Been Tested?

Please mark the following checks done

• Schema validated using JSON Schema template.schema
• Template functionality checked using Online Editor
• Template is checked using template linter
• Template file name follows the pattern <providerId>.<serviceId>.json

Example variable values

<-- to make review process easier please provide example set of variable values for this template -->

<-- Example: -->

var1: aaa
var2: foo.com

<-- Or provide the whole testData object from the Online Editor after testing and using "Add as test" button -->

"testData": {
    "testset": {
      "variables": {
        "domain": "example.com",
        "host": "foo",
        "example": "bar"
      },
      "results": [
        {
          "type": "TXT",
          "name": "foo",
          "ttl": 86400,
          "data": "\"bar\""
        }
      ]
    }
  }

[github-actions]

Linter OK:

Linter result for vercel.com.website.json

[pawel-kow]

lgtm!