Add notes option to description types, landing page a11y

[jennur]

Closes https://github.com/zenodo/rdm-project/issues/229

• Adds "Notes" option in additional description types
• Makes heading levels h2-h4 semibold
• Removes the secondary color definition, as the reason for adding it was fixed in invenioRDM (new-buttons: remove secondary class from buttons inveniosoftware/invenio-oauth2server#253 button colors on "profile settings/applications"), and it was causing wrong color on tabs.
• Stacks "upload" and "published" info on "Recent uploads" record items (long texts were smashing all other content on the same line) - matches the layout in current Zenodo
• Fixes arrow icon + accessibility improvements on files accordion
• Adds favicon