Fix warnings when run the dev environment to a theme

[javierlopezdeancos]

Probably this is because we are running 2 environments if we execute npm run dev:theme:caramel

[1] [0] ../../core/src/default-theme/default.css
[1] [0] 227:2	⚠  Can't read asset file "/Users/javierlopezdeancos/Code/higgsboson.org/higgsboson/packages/themes/caramel/src/assets/svg/logo-light.svg". Ignoring. [postcss-copy-assets]
[1] [0] 288:4	⚠  Can't read asset file "/Users/javierlopezdeancos/Code/higgsboson.org/higgsboson/packages/themes/caramel/src/assets/svg/logo-dark.svg". Ignoring. [postcss-copy-assets]
[1] [0] 
[1] [0]  ⚠ 2 problems (0 errors, 2 warnings)
[1] [0] 
[1] [0] Finished src/index.css in 197 ms

Technically, we are running under the hood 2 dev environments,

• the higgsboson core dev environment
• the caramel theme dev environment

So probably reference take some collisions.
Probably the best way to proceed is not run automagically those 2 env under the hood and leave the developer the responsibility to run them in separate shell processes?