Support FA shims

[javier-godoy]

Investigate how to support Font Awesome shims.

Shims helps to achieve compatibility with Font Awesome 4 icon references by mapping the legacy icon names to FA Version 5/6 names

What shims can do

(From https://fontawesome.com/docs/apis/graphql/objects#shim)

1. Some icons that appear in Font Awesome 4 have been renamed. A shim can map the Version 4 icon name to the Version 5/6 icon name automatically.

2. For some Version 4 icons, their visual appearance matches the Regular style better than the Solid style. A shim can automatically change these icons to use the Regular style.

3. Font Awesome 5/6 puts all brand-related icons into a separate Brands style; Font Awesome 4 did not. A shim can map Version 4 brand icons into the Font Awesome 5 Brand style.