Move resource library into resources nav (and drop events)

[traceyljohnson]

• Add a new link to the Resources dropdown for "Resources"
  • The new link headline should be: Resources
  • Underneath that, it should say: Videos, guides, content, and more
  • Reuse the existing 'Docs' icon for this link
• Remove "Docs" from the Resources dropdown
• Remove "Events" from the Resources dropdown

After above changes, the new order of the resources menu should be:

• Support Forum (capitalize the F so we're consistent)
• Resources
• Blog
• Customer Stories
• Community
• Sourcegraph Labs