Feat/update all transactional email templates

[chickenn00dle]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

This PR updates the remaining transactional email template designs to match the updates done to the OTP email (#3032, #3033, and #3034)

Account verification:

Reset password:

Receipt:

Account deletion:

Subscription/Donation cancellation:

(OTP will have already been updated at this point)

Note: I believe we will be removing the Magic Link template in favor of always using the OTP. At least based on the Figma here: https://www.figma.com/file/c6T1goPQpkchdh7XBAM6aH/Reader-Activation-System?type=design&node-id=1589-35127&mode=design&t=1gF6i52UIhsMYAk3-0

I will confirm this and remove in a follow-up PR if this is the case. Regardless, I've updated the design for this template in this PR anyway, but currently there is no way to trigger it via the UI.

How to test the changes in this Pull Request:

1. Go to Newspack > Engagement > Show Advanced Settings > Transactional Email Content, then trash each of the emails shown here via the edit button (should be every one mentioned above except for the receipt template). This is so our default templates can be used for emails.
2. Go to Newspack > Reader Revenue > Emails, then trash the receipt email via the edit button.
3. Trigger each of the emails, then view them and verify they look as pictured above. You can trigger each email as follows:

• Account verification - As a logged out user, sign up for a new account. Once logged in, go to My Account and select the Send me a link option to send a verification email
• Password reset - Once verified, go back to My Account and select the Create a Password link
• Receipt - Purchase a donation via the donation block. You will need to set up the block on any post or page to do this
• Account deletion - Go to My Account and select the Delete Account button
• Receipt - Purchase a recurring donation or subscription product
• Subscription/Donation Cancellation - Cancel the recurring donation or subscription via My Account

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[chickenn00dle]

Taking this back to WIP since I was looking at the wrong email designs 🤦

[chickenn00dle]

Ready for review again.

[adekbadek]

I've found a bug when testing, but it's not introduced by this PR. Noted here: #3056 (review).

[matticbot]

🎉 This PR is included in version 3.8.0-epic-ras-acc.2 🎉

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[matticbot]

🎉 This PR is included in version 3.9.0-epic-ras-acc.1 🎉

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[matticbot]

🎉 This PR is included in version 4.1.0-epic-ras-acc.1 🎉

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[matticbot]

🎉 This PR is included in version 4.2.0-epic-ras-acc.1 🎉

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[matticbot]

🎉 This PR is included in version 4.4.0-epic-ras-acc.1 🎉

The release is available on GitHub release

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