Add description for "Running Tasks"

[fanzhidongyzby]

中： 执行中任务：正在执行的任务列表，可以在此进行停止任务。运行完成的任务不在此展示。

EN： Running Tasks: A list of tasks currently being executed, where tasks can be stopped. Tasks that have been completed are not displayed here.

[qishipengqsp]

Review this issue both in the two versions of web interface:

1. The new browser is yet under construction. Check this.
2. The legacy web. Add the description to the legacy web.