Describe Vim-like search in review UI documentation

Change-Id: I9a99aba1579e0188e4e9aa7c050c6d6c32817e14
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

Documentation/user-review-ui.txt

diff --git a/Documentation/user-review-ui.txt b/Documentation/user-review-ui.txt
index 813cd0e..12b7ff4 100644
--- a/Documentation/user-review-ui.txt
+++ b/Documentation/user-review-ui.txt
@@ -871,6 +871,28 @@
 
 image::images/user-review-ui-side-by-side-diff-screen-file-level-commented.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-file-level-commented.png"]
 
+[[search]]
+=== Search
+
+For searching within a patch file, a Vim-like search is supported.
+Typing `/` opens the search box. Typing in the search box immediately
+highlights matches in the patch file with a yellow background. Using
+JavaScript regular expressions in the search term is supported. The
+search is case insensitive. After confirming the search by `ENTER` one
+can navigate between the matches by `n` / `N` to go to the next /
+previous match. Skipped lines are automatically expanded if they
+contain a match and one navigates to it.
+
+For additional possibilities to search please check the
+link:http://www.vim.org/docs.php[Vim documentation]. There are other
+useful ways to search, e.g. while the cursor is on a word, pressing `*`
+or `#` searches for the next or previous occurrence of the word.
+
+Searching by `Ctrl-F` finds matches only in the visible area of the
+screen unless the link:#render[Render] diff preference is set to `Slow`.
+
+image::images/user-review-ui-side-by-side-diff-screen-search.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-search.png"]
+
 [[diff-preferences]]
 === Diff Preferences