docs: additional v1 updates

docs: also add concrete example for offset recreating placement: 'center'

Author: atomiks

website/pages/docs/computePosition.mdx

@@ -173,15 +173,15 @@ extend the behavior of the library.
 ## Return value
 
 ```ts
-type ComputePositionReturn = {
+interface ComputePositionReturn {
   x: number;
   y: number;
   // The stateful placement, which can be different
   // from the initial `placement` passed as options
   placement: Placement;
   strategy: Strategy;
   middlewareData: MiddlewareData;
-};
+}
 ```
 
 ## Updating

website/pages/docs/inline.mdx

@@ -97,10 +97,5 @@ can be passed in to choose a rect.
 
 default: `2{:js}`
 
-> Experimental
-
 This describes the padding around a disjoined rect when choosing
 it.
-
-This option's configurability is currently experimental and may
-be removed by v1. You likely don't need to change the default.

website/pages/docs/offset.mdx

@@ -58,11 +58,9 @@ interface AxesOffsets {
 type Options =
   | number
   | AxesOffsets
-  | (({
-      reference: Rect,
-      floating: Rect,
-      placement: Placement,
-    }) => number | AxesOffsets);
+  | ((
+      middlewareArguments: MiddlewareArguments
+    ) => number | AxesOffsets);
 ```
 
 A number represents the distance (gutter or margin) between the
@@ -145,6 +143,12 @@ values enables the ability to "inset" the floating element such
 that it is positioned on top of the reference element in some
 fashion.
 
-This is useful for UI components such as select dropdowns where
-it should be positioned relative to an item inside the dropdown
-list.
+For instance, if you wanted to mimic something like
+`'center'{:js}` for `placement{:.objectKey}` (with default
+placement):
+
+```js
+offset(({rects}) => {
+  return -rects.reference.height / 2 - rects.floating.height / 2;
+});
+```