Update 'Support' in header and 'Get Involved' icons to reference project's Open Collective page

[scottAnselmo]

Problem: Currently the 'Support' header and the icons in 'Get Involved' only reference Patreon, limiting discoverability of supporting through Open Collective

Solution:

• Update Support header to have a two item dropdown that links to Patreon and Open Collective pages, or directs to a Support landing page that has links to both. The former may be preferable as it minimizes site code and translation strings
• Update the 'Get Involved' section in the footer to include an icon for Open Collective. If the current stylesheet does not support an Open Collective icon, suggest referencing this stylesheet to generate the icon: https://css.gg/open-collective