Move optional attribute documentation (#369)

docs/content/elements-attributes.md

@@ -84,25 +84,6 @@ html! {
 # ;
 ```
 
-## Optional attributes: `title=[Some("value")]`
-
-Add optional attributes to an element using `attr=[value]` syntax, with *square* brackets.
-These are only rendered if the value is `Some<T>`, and entirely omitted if the value is `None`.
-
-```rust
-# let _ = maud::
-html! {
-    p title=[Some("Good password")] { "Correct horse" }
-
-    @let value = Some(42);
-    input value=[value];
-
-    @let title: Option<&str> = None;
-    p title=[title] { "Battery staple" }
-}
-# ;
-```
-
 ## Empty attributes: `checked`
 
 Declare an empty attribute by omitting the value.

docs/content/splices-toggles.md

@@ -142,3 +142,22 @@ html! {
 }
 # ;
 ```
+
+### Optional attributes with values: `title=[Some("value")]`
+
+Add optional attributes to an element using `attr=[value]` syntax, with *square* brackets.
+These are only rendered if the value is `Some<T>`, and entirely omitted if the value is `None`.
+
+```rust
+# let _ = maud::
+html! {
+    p title=[Some("Good password")] { "Correct horse" }
+
+    @let value = Some(42);
+    input value=[value];
+
+    @let title: Option<&str> = None;
+    p title=[title] { "Battery staple" }
+}
+# ;
+```