feat: add allowPopups option

[azu]

This PR aim to add allowPopups option(disabled by default).

sandbox attribute was introduces in #1222
sandbox apply allow list model. So, if any sandbox attributes exists, disable default features like allow-popups.

• Play safely in sandboxed IFrames - HTML5 Rocks
• CSP: sandbox - HTTP | MDN

Currently, we can not open external link from epub content.

For example, Click the link like<a href="https://example.com" target="_blank">link</a> and throw an error

Blocked opening 'https://example.com' in a new window because the request was made in a sandboxed frame whose 'allow-popups' permission is not set.

The allowPopups allow user open the link.

Test Plan

1. Open http://localhost:8080/examples/input.html
2. Load epub content that include external link
3. Click the link in the cotent

[fchasen]

Thanks, this looks great.

I'm thinking in the future we should handle all the links from the Rendition (currently only internal links work that way) but this option should still be useful.

[azu]

Thanks to merge!
0963efe

Is 0.3.93 published into npm?

❯ npm info epubjs

epubjs@0.3.92 | BSD-2-Clause | deps: 9 | versions: 107

[fchasen]

Had an issue with 2 factor auth, published now!

[azu]

Thanks!