Add Sumo Logic RUM snippet to docs site

[kimsauce]

Purpose of this pull request

Do not merge until @vfalconisumo approves

Add Real User Monitoring (RUM) script to the head to help diagnose bundle issues on the docs site.

Test plan

• Verify the site builds successfully
• Confirm the RUM script appears in the of the rendered page
• Check the browser Network tab for requests to rum.sumologic.com

Select the type of change

• Minor Changes - Typos, formatting, slight revisions
• Update Content - Revisions, updating sections
• New Content - New features, sections, pages, tutorials
• Site and Tools - .clabot, version updates, maintenance, dependencies, new packages for the site (Docusaurus, Gatsby, React, etc.)

Ticket (if applicable)

https://sumologic.atlassian.net/browse/DOCS-1373