add: customizable what slug

src/routes.rs

@@ -43,6 +43,10 @@ fn default_context(data: &DataClient) -> Context {
         &std::env::var("NAME").unwrap_or("Attobin".to_string()),
     );
     ctx.insert("tetratto", &data.host);
+    ctx.insert(
+        "what_page_slug",
+        &std::env::var("WHAT_SLUG").unwrap_or("what".to_string()),
+    );
     ctx
 }