Add OpenSpeedTest Rock-on

[phillxnet]

Available in an official docker container, this looks to be a nice fit for our Appliance NAS settings. Primarily to facilitate network testing, outside of 'share' service, to help with diagnosing network issues or to confirm network hardware/driver capabilities are as-expected.

Website: https://openspeedtest.com/

A more accessible option to desktop client users, who are reasonably expected to have a browser installed, than iperf etc.

[phillxnet]

Docker image doc section on main website: https://openspeedtest.com/selfhosted-speedtest#Source-Code-Docker