Hyphenation CSS

Dear hugo community,

I’m still pretty new to website design and want to implement automatic hyphenation to all my website content.

I designed my homepage using the Zen theme: zen-theme.

To achieve my goal I If first create a CSS (called hyphen.css) (as described here: mozilla-dev) in the layouts folder.
Then a linking to the CSS is added into the section of baseof.html:

< link rel=“stylesheet” type=“css” href=“/layouts/_default/hyphen.css”>

Unfortunately, it won’t work when applying in the markdown files by specifying the text with:

< p lang=“en” class=“auto”>

Is there a way to implement hyphenation all over the website?

Thanks in advance!