Adding branding resources

[dgkf]

Linking to a few brand elements you might choose to incorporate.

• logo
• colors

Objective

• Reports receive R Validation Hub branding by default
• And can be customized to use organization branding (I'd still like to mention R Validation Hub somewhere, but we should let brands customize the major design elements)

[llrs-roche]

This should be used for:

• Presentation of the report #18 (currently work in progress on Improve the looks of the report  #19)

[llrs-roche]

I see this was moved to Planning @dgkf. On checking the linked PR I think we incorporated everything mentioned here.

In addition, by using quarto users could use the _brand.yml file to specify logo and colors. But I haven't verified it.
Do you have something else in mind too?

[Zhenglei-BCS]

Will propose changes from the draft pull: #39