Support enhanced conversions

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Allow additional attributes to be passed in and hashed for [enhanced conversions](https://support.google.com/google-ads/answer/13258081). This will improve matching for ads by passing in known data about the user.

The Google documentation defines what fields can be passed in, and they could be pre-hashed with SHA256. The exact data format of the API request isn't clear from the docs, but in the validate your implementation section, it mentions the `em` parameter will be added:

> Look for a parameter “em” with a hashed string as the value. The value should start with “tv.1~em” followed by a long string of characters. If you see the "em" parameter, this means that the enhanced conversions tag is picking up and hashing the enhanced_conversion_data object.

Start with the linked Google enhanced conversions documentation and its “validate your implementation” section, focusing on the allowed fields, SHA256 preprocessing, and the `em` parameter format. Compare those requirements with the existing TypeScript Google Ads component, then confirm done when supported attributes are passed in the documented format and the resulting request exposes the expected `em` value.

Written by the indexing model from the issue text.