add documentation and changeset

Signed-off-by: Juan Pablo Garcia Ripa <sarabadu@gmail.com>

.changeset/eight-insects-tan.md

@@ -2,4 +2,5 @@
 '@backstage/core-components': patch
 ---
 
-Add `useContent` hook to have a reference to the current main content element
+- Add `useContent` hook to have a reference to the current main content element
+- Sets the main content reference on `Content` component

.changeset/eleven-sloths-shake.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-search': patch
+---
+
+Removes the focus from the sidebar and focus the main content after select one search result or navigate to the search result list