App-2589 - Markdown link in rule description

[jpipkin1]

Purpose of this pull request

This pull request (PR) adds a note to the "with the description" field in Cloud SIEM rule articles describing how to add a markdown link. The note will appear here:

• https://help.sumologic.com/docs/cse/rules/write-match-rule/#configure-then-create-a-signal-settings
• https://help.sumologic.com/docs/cse/rules/write-chain-rule/#configure-then-create-a-signal-settings
• https://help.sumologic.com/docs/cse/rules/write-aggregation-rule/#configure-then-create-a-signal-settings
• https://help.sumologic.com/docs/cse/rules/write-threshold-rule/#configure-then-create-a-signal-settings

Issue number: APP-2589

Select the type of change:

• Minor Changes - Typos, formatting, slight revisions
• Update Content - Revisions and updating sections
• New Content - New features, sections, pages, tutorials
• Site and Tools - Updates, maintenance, and new packages for the site, Gatsby, React, etc

[jpipkin1]

Thanks, @kimsauce!