Document sprintf usage

What does this MR do?

This documents the gl-sprintf component to explain how we should go about component interpolation when translating strings in Vue.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Closes #21344 (closed)