🐛 Fix relative path to js/open-in-new-tab.js`

[ebouchut]

My attempt to fix #10

See #10 for details.

[JakubAndrysek]

Do I need these changes? Is it better to add this js file first, or is the problem that, in some cases, the append method doesn't work?

Thank you for your work; I am just figuring out why these changes are needed.

Have a nice day

[ebouchut]

Does not Work

It does not work when deployed on Github-Pages (with a subfolder trio-docs in my case):

Works

It works in:

• locally with mkdocs serve

With the fix it works locally and when deployed on GH-Pages:

[ebouchut]

@JakubAndrysek
For whatever reason, adding js/open-in-new-tab.js first makes it work.
This is why I need your guidance here.
I do not get the reason for now.