fix(template): update template.pug to allow popups in the html version

[nahtnam]

Checklist

Same issue with the HTML preview as the text preview. Fixes #36

• I have ensured my pull request is not behind the main or master branch of the original repository.
• I have rebased all commits where necessary so that reviewing this pull request can be done without having to merge it first.
• I have written a commit message that passes commitlint linting.
• I have ensured that my code changes pass linting tests.
• I have ensured that my code changes pass unit tests.
• I have described my pull request and the reasons for code changes along with context if necessary.

[nahtnam]

cc @titanism, this is ready!

[titanism]

v3.1.0 released to npm

https://github.com/forwardemail/test-preview-emails-cross-browsers-ios-simulator-nodejs-javascript/releases/tag/v3.1.0

thank you @nahtnam 🙏

we use this in @forwardemail and this will be a nice addition