Improve label and text wrapping (#14113)

* Improve label wrapping

- Adjust issue list styles so labels can wrap on the same line as the
  text. This relies on `display: inline` with the HTML whitespace being
  used as the separator.
- Add global word-break: break-word. This should generally avoid text
  overflows in various places.

* add whitespace to history labels

* use overflow-wrap

* restore word-break rules

* use correct pre

* use better selector for middle align

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

web_src/less/_base.less

@@ -176,6 +176,7 @@ body {
   overflow-y: auto;
   display: flex;
   flex-direction: column;
+  overflow-wrap: break-word;
 }
 
 img {