[SYS] Add mDNS discovery

[1technophile]

Description:

So as to enable access to the WebUI with the gateway name

Checklist:

• The pull request is done against the latest development branch
• Only one feature/fix was added per PR and the code change compiles without warnings
• I accept the DCO.

[NorthernMan54]

Not for OMG but I use this hosted locally to find my Tasmota and openBK devices

https://github.com/iotreboot/TasUI

[1technophile]

This is a cool project, does it still work with Tasmota, I see that there was a lot of security discussion around it arendst/Tasmota#6767

[NorthernMan54]

I held my tasmota devices at the version prior to that being implemented, so it works for me

im not a CORS expert, but I think a local implementation resolves the security issue.

I only mention that package, as Tasmota got rid of mdns years ago due to stability issues

arendst/Tasmota#11414