docs: emoji cheat sheet with shortcodes

What does this MR do?

Change the emoji cheat sheet in the markdown description to one with ::-shortcodes to copy and paste.

Related issues

Closes #42672 (closed)

Author's checklist

• Apply the correct labels and milestone
• Crosslink the document from the higher-level index
• Crosslink the document from other subject-related docs
• Feature moving tiers? Make sure the change is also reflected in features.yml
• Correctly apply the product badges and tiers
• [ ] Port the MR to EE (or backport from CE): always recommended, required when the ee-compat-check job fails

Review checklist

• Your team's review (required)
• PM's review (recommended, but not a blocker)
• Technical writer's review (required)
• [ ] Merge the EE-MR first, CE-MR afterwards

/label ~Documentation