Metadata: reported location is wrong when error encountered in first attribute

[anderseknert]

# METADATA
# description: `foo` bars
# title: foo
package foo

Backticks are apparently not allowed as the first character of an unquoted YAML string, but that wasn't obvious to me as the error reported is:

{
  "errors": [
    {
      "message": "yaml: found character that cannot start any token",
      "code": "rego_parse_error",
      "location": {
        "file": "p.rego",
        "row": 1,
        "col": 1
      },
      "details": {
        "line": "# METADATA",
        "idx": 0
      }
    }
  ]
}

However, if we move the location of the error to a later line, the location is reported correctly:

# METADATA
# title: foo
# description: `foo` bars
package foo

{
  "errors": [
    {
      "message": "yaml: line 2: found character that cannot start any token",
      "code": "rego_parse_error",
      "location": {
        "file": "p.rego",
        "row": 3,
        "col": 1
      },
      "details": {
        "line": "# description: `foo` bars",
        "idx": 0
      }
    }
  ]
}

[stale]

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