feat(collapse): clean up documentation

Closes #5194

Author: nonplus

src/collapse/docs/readme.md

@@ -8,26 +8,22 @@
   _(Default: `false`)_ -
   Whether the element should be collapsed or not.
 
-* `collapsing`
-  <small class="badge">$</small>
-  _(Default: `none`)_ -
-  A callback function that gets fired before the element begins collapsing.
-  If the function returns a promise, animation won't start until the promise resolves.
+* `collapsing()`
+  <small class="badge">$</small> -
+  An optional expression called before the element begins collapsing.
+  If the expression returns a promise, animation won't start until the promise resolves.
   If the returned promise is rejected, collapsing will be cancelled.
 
-* `collapsed`
-  <small class="badge">$</small>
-  _(Default: `none`)_ -
-  A callback function that gets fired after the element finished collapsing.
+* `collapsed()`
+  <small class="badge">$</small> -
+  An optional expression called after the element finished collapsing.
 
-* `expanding`
-  <small class="badge">$</small>
-  _(Default: `none`)_ -
-  A callback function that gets fired before the element begins expanding.
-  If the function returns a promise, animation won't start until the promise resolves.
+* `expanding()`
+  <small class="badge">$</small> -
+  An optional expression called before the element begins expanding.
+  If the expression returns a promise, animation won't start until the promise resolves.
   If the returned promise is rejected, expanding will be cancelled.
 
-* `expanded`
-  <small class="badge">$</small>
-  _(Default: `none`)_ -
-  A callback function that gets fired after the element finished expanding.
+* `expanded()`
+  <small class="badge">$</small> -
+  An optional expression called after the element finished expanding.