Review: 9 articles exist in translations but not in English source

[zoyth]

Orphan translations

These articles exist in ES or FR-CA but have no corresponding EN source article. They appear to be migration artifacts from Zendesk. Please decide whether to:

• Keep: Create the EN source article (and they become translations)
• Remove: Delete the orphan files

In ES only (no EN equivalent):

• es/docs/audience-building/adding-a-subscription-form-to-your-website.md
• es/docs/billing/selecting-the-right-plan-and-pricing-for-your-email-marketing-needs.md
• es/docs/billing/update-your-billing-information.md

In FR-CA only (no EN equivalent):

• fr-ca/best-practices/deliverability/avoiding-spam-traps.md
• fr-ca/best-practices/deliverability/opens-clicks-bounces-unsubscribes-and-spam-what-are-good-rates.md
• fr-ca/best-practices/deliverability/optimizing-your-deliverability.md
• fr-ca/best-practices/deliverability/permission-marketing.md
• fr-ca/best-practices/deliverability/spam-complaints-and-how-to-avoid-them.md
• fr-ca/best-practices/deliverability/use-my-own-domain-in-the-sender-email-address-why.md
• fr-ca/best-practices/deliverability/why-permission-from-contacts-is-necessary.md

In both ES and FR-CA (no EN equivalent):

• docs/audience-building/adding-a-subscription-form-to-your-website.md
• docs/billing/update-your-billing-information.md