Add documentation for VCS hooks config

README.md

@@ -582,6 +582,9 @@ customization is provided via:
 |`POWERLEVEL9K_CHANGESET_HASH_LENGTH`|`12`|How many characters of the hash / changeset to display in the segment.|
 |`POWERLEVEL9K_VCS_SHOW_SUBMODULE_DIRTY`|`true`|Set to `false` to not reflect submodule status in the top-level repository prompt.|
 |`POWERLEVEL9K_VCS_HIDE_TAGS`|`false`|Set to `true` to stop tags being displayed in the segment.|
+|`POWERLEVEL9K_VCS_GIT_HOOKS`|`(vcs-detect-changes git-untracked git-aheadbehind git-stash git-remotebranch git-tagname)`|Layout of the segment for git repositories.|
+|`POWERLEVEL9K_VCS_HG_HOOKS`|`(vcs-detect-changes)`|Layout of the segment for Mercurial repositories.|
+|`POWERLEVEL9K_VCS_SVN_HOOKS`|`(vcs-detect-changes svn-detect-changes)`|Layout of the segment for SVN repositories.|
 
 
 ##### vcs symbols