chore: fix eslint issues in ee & email packages

[mattinannt]

What does this PR do?

chore: auto-fix eslint issues in ee package, enable linting in ee package, enforce tighter rules in the email package and solve typescript issues

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| Name | Status | Preview | Comments | Updated (UTC) | | :--- | :----- | :------ | :------- | :------ | | **formbricks-cloud** | ⬜️ Ignored ([Inspect](https://vercel.com/formbricks/formbricks-cloud/9Gkdy2ttnQRbnrttARjafPqMJwft)) | [Visit Preview](https://formbricks-cloud-git-feature-eslint-ee-package-formbricks.vercel.app) | | Jun 7, 2024 11:16am | | **formbricks-docs** | ⬜️ Ignored ([Inspect](https://vercel.com/formbricks/formbricks-docs/8QsnSqpNC3VqPvLJv6JFmGkhWfGM)) | [Visit Preview](https://formbricks-docs-git-feature-eslint-ee-package-formbricks.vercel.app) | | Jun 7, 2024 11:16am |

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