Description

Added a new documentation entry for the size() method of Java queues.
The file out_size.md contains:

• Front‑matter with metadata (title, description, subjects, tags, catalog content).
• A concise explanation of what size() does.
• Syntax block, Java example, and a Codebyte block using the required codebyte/java format.

Issue Solved

Link to the issue discussion:
#7368 (comment)

Type of Change

• Adding a new entry

Checklist

• [v] All writings are my own.
• [v] My entry follows the Codecademy Docs style guide.
• [v] My changes generate no new warnings.
• [v] I have performed a self-review of my own writing and code.
• [v] I have checked my entry and corrected any misspellings.
• [v] I have made corresponding changes to the documentation if needed.
• [v] I have confirmed my changes are not being pushed from my forked main branch.
• [v] I have confirmed that I'm pushing from a new branch named after the changes I'm making.
• [v] I have linked any issues that are relevant to this PR in the Issues Solved section.