[NTG-context] Fonts from various .otf to work with \bold, \emph, \bf, \bfa ...

[context at vivaldi.net]

Hello,

although font switching used to be discussed here and I studied wiki 
about font changing, I don't switch fonts in ConTeXt very often and my 
"maximum" font change was provided by \setupbodyfont[(e.g. termes)].

Now I am in the situation that I need to use fonts defined in:

   work-sans.bold.otf
   work-sans.bold-italic.otf
   work-sans.light.otf
   work-sans.light-italic.otf

(all from https://www.1001fonts.com/work-sans-font.html)

so that:

- normal text and math (nothing special - just subscripts) would be 
typeset with work-sans.light.otf
- \bold (\bf) would use work-sans.bold.otf,
- \emph (\em and \it) would use work-sans.light-italic.otf,
- \bi would use work-sans.bold-italic.otf
- also commands \bfa, \bfc, ... would use work-sans.bold.otf scaled 
somehow (probably by multiples of 1.2).

Some help setting it up and making it work would be appreciated...

Best regards,

Lukas