Add link to Marketing materials

Why is this change being made?

This change is being made to surface a useful collection of content that is strictly for internal use only as it has many ungated links to white papers, webcasts, and protected analyst content. This resource will help our salespeople to educate themselves, share gated content on social media, and ungated links to their existing clients throughout the sales process.

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
• Assign this change to the correct DRI
  • If the change relates to any part of the project other than updates to content and/or data files (e.g. team.yml) please make sure to ping @gl-static-site-editor in a comment for a review and merge.
  • If the DRI for the page/s being updated isn't immediate clear, then assign it to your manager.
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies

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