add command time duration plugin (#1683)

docs/themes-list/barbuk.rst

@@ -38,6 +38,7 @@ Default theme glyphs
    BARBUK_SVN_CHAR='⑆ '
    BARBUK_EXIT_CODE_ICON=' '
    BARBUK_PYTHON_VENV_CHAR=' '
+   BARBUK_COMMAND_DURATION_ICON='  '
 
 Customize glyphs
 ^^^^^^^^^^^^^^^^
@@ -92,6 +93,11 @@ Please refer to the following documentation for more information:
    EOF
    chmod 400 /etc/sudoers.d/keepenv
 
+Command duration
+----------------
+
+See :ref:`Command duration <command_duration>`.
+
 Examples
 --------
 
@@ -122,3 +128,11 @@ Python venv
 .. code-block:: bash
 
      flask ~/test on  master ✓ ❯
+
+Command duration
+^^^^^^^^^^^^^^^^
+
+.. code-block:: bash
+
+   # sleep 3s
+   user@hostname in  ~/bash-it on  master ✓  3.2s ❯