Ability to add `id` property to `{{input_email}}`

Issue Summary

Currently, the email subscribe_form and/or input_email (in beta) do not support the ability to add an ID property. This means that it is not possible to provide a label to this input element. This impacts the accessibility pretty significantly, especially to screen readers.

Steps to Reproduce

1. Via https://themes.ghost.org/docs/subscribers — {{input_email}} currently accepts:
   • class
   • placeholder
   • value
   • autofocus
2. Adding the attribute id produces no result

While some can/should be able to chose not to label the input element, to do so is not really a best practice. In the future some groups may not be able to use this feature because it does not comply with their accessibility needs, which would be unfortunate

Technical details:

• Ghost Version: 1.12.0
• Node Version: N/A
• Browser/OS: N/A
• Database: N/A

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Personally I think it would be preferable to have a label for the input in subscribe_form, and giving the ability for users to remove it by way of creating their own template partial. While not labeling them by default may look cooler, It does exclude some users which makes me 😢 The current implementation is also not particularly clear to sighted users.

[naz]

@kirrg001 grabbing this one 😉

[whmii]

thanks @kirrg001 Nice work!! This was out of my wheelhouse so couldn’t really help but glad to see it added. Muchos internet and a11y points to you 🤠