[Term Entry] Javascript Window function: scrollBy()

[codecademy-docs]

Reason/inspiration (optional)

We would like a new term entry for JavaScript's Window Function - scrollBy()

The entry should go in a new file in docs/content/javascript/concepts/window/terms/scrollBy/scrollBy.md

The entry should:

• Have an introduction to the function
• Have a syntax section illustrating the scrollBy() function.
• An example showing how to use this function.

Please refer to the term template, content standards, and style guide when working on the PR for this issue.

Entry Type (select all that apply)

New Term for Existing Concept Entry

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