Add ability to set breathe in hold duration

[MattChubb]

I wanted the ability to configure the breathe in hold to something other than 15sec, so I added it as a configurable setting with room to add others there later. Not sure about the layout but it's workable.

[MattChubb]

I also noticed the CICD is failing. I think I need to set something up for gh-pages to work properly?

[Koenkk]

2 remarks:

• I think the settings migration is not working correctly (NAN values)
• There are no labels for the input boxes, now it's unclear what the value is for