RHIDP-1583: Add details for favicon customization

[abrennan89]

Versions:
1.2+

Jira link:

• https://issues.redhat.com/browse/RHIDP-1583

Preview link:

• https://redhat-developer.github.io/red-hat-developers-documentation-rhdh/pr-280/getting-started-rhdh/#ref-additional-rhdh-customizations_rhdh-getting-started

Reviews:

• SME: @invincibleJai
• QE: TBA
• Peer review: TBA

Notes
There is a separate PR for 1.1.x that implements the changes from this PR as well as the improvements from #260 but without the sidebar logo width, which only applies for 1.2+.

1.1.x PR: #281

[rhdh-bot]

PR Preview: https://redhat-developer.github.io/red-hat-developers-documentation-rhdh/pr-280/

[rhdh-bot]

PR Preview: https://redhat-developer.github.io/red-hat-developers-documentation-rhdh/pr-280/

[invincibleJai]

Thanks @abrennan89

Favicon customization is not working as expected, we have a ticket for this here janus-idp/backstage-showcase#777

So I don't think we should be capturing this as part of docs and can add it in known issues may be.

[nickboldt]

add it in known issues

@invincibleJai is this something we're looking to fix in 1.3? If so then yeah, a KI makes sense; but if it's not really on the radar to fix it, then do we want to expose a KI that we'l have to carry forward for a few releases?

[abrennan89]

Closing PR since this functionality currently isn't working