[FEA] Highlight Additional Package Name

[nv-rliu]

Is your feature request related to a problem? Please describe.

This is a suggested feature mentioned in this thread of #536.

Highlight the Additional Package names separate from their version pinning.

Describe the solution you'd like

The following function needs to be refactored to support this feature.

if (this.active_additional_packages.length) {
    add_pkgs_ln = indentation + this.active_additional_packages
    .map(pkg => this.highlightCondaPkg(this.getAdditionalPkgName(pkg)))
        .join(" ");
}

Describe alternatives you've considered
Nothing yet. The proposed change just requires some minimal design changes.

Additional context
This was filed as a separate issue so #536 could be merged.