Creating SQL term page for equals to operator

[selenahuang017]

Description

Adding SQL Equal to operator to SQL concepts under docs/content/sql/concepts/operators/terms/equal-to/equal-to.md.

Issue Solved

Addresses issue: https://github.com/Codecademy/docs/issues/4849

Type of Change

• Adding a new entry

Checklist

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