message: add fetchMembers to the overview list in readme
diff: @@ -170,7 +170,7 @@ This section will list out all the available methods and functionality in the li
  - .swapRoles(rolePositons)
  - .getPruneCount(days)
  - .pruneMembers(days)
  -// - fetchAllMembers()
  +- .fetchMembers(options)
  - .getAuditLogs(options)
  - .getEmbed()
  - .editEmbed(enabled, channel_id)
  