Fix missing images on English pages

Hugo only auto-shares page-bundle resources across translations when
each language has its own content directory; with filename-based
translation (index.fr.md / index.en.md in the same folder) a resource
with no language code is assigned to the default language only. Add
.en.-suffixed copies of every image referenced from English pages and
point the English markdown at them.

content/documentation/securité/cadenas_vert/ssl.en.md

@@ -10,7 +10,7 @@ cascade:
 
 You've seen it thousands of times, haven't you? That little **green padlock** (or sometimes gray, depending on your browser and the site) that shows up next to a website's address in your navigation bar. You click on it, you look at it, you think "cool, it's secure," and you move on.
 
-![Certificat](certificat.png)
+![Certificat](certificat.en.png)
 
 But... do you really know what it means? 🤔 All the **mechanics that kick in** just so this little symbol appears? It's much more than a simple icon! It's the visible part of an iceberg. \
 **So, what's our mission today? 🚀**