Did you understand enough of the description to decide whether to use the extension? If yes, then the description is enough as it is.
And if the project becomes popular, then native speakers will likely eventually volunteer to edit the documentation including any landing page.
I promise, I’m not being passive-aggressive or sarcastic or anything here. I am genuinely unsure what makes this such a significant oversight and even more surprised at all the upvotes.
On the contrary, I find it more compelling to read such a description in obviously non-native English, because I would expect that from a person who genuinely needs a more-convenient translator (mostly from English to their native language, because so much of the web is in English) in their browser. Who better to build one?