[Term Entry] Dart Maps .forEach()

[Codecademy-docs]

Reason/inspiration (optional)

"We would like a new term entry under Dart Maps for the Dart Map .length() method.
Provide the entry in a markdown file under docs/content/dart/concepts/map/terms/length/length.md

The entry should
- Have an introductory paragraph about what the method is and does.
- A syntax section with a pseudo code block with an explanation of it.
- An example showing the method in use.

Please refer to the concept entry templates, content standards, and markdown 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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[Aaron Sanchez]

Hello!
I would like to tackle this issue if possible!
Thank you!

[Ishwari Garge]

@aaron-ross-sanchez You're assigned!🎉You can look through the Contribution Guide to know more about contributing to Codecademy Docs. Check out the Content Standards and Style Guide, they’ll help you with creating your entry.

I see this is your first time contributing to Codecademy Docs. How did you find out about us?

[Aaron Sanchez]

Thank you! I found out about this repository through the good first issues website: https://goodfirstissues.com/index.html

[Aaron Sanchez]

@ishg-153 I just wanted to check to see that this was for the Dart Map .forEach() method, and not .length()

"We would like a new term entry under Dart Maps for the Dart Map .length() method.