[docs] Added "Running Scripts Locally" from Notion docs to dev_environment docs.

Summary: The "Running Scripts Locally" note was independent from the dev_environment docs. I unified them, and added it to the "Development" section.

Test Plan: N/A

Reviewers: atul, palys-swm, ashoat

Reviewed By: atul, ashoat

Subscribers: ashoat, palys-swm, Adrian, karol-bisztyga, benschac, boristopalov

Differential Revision: https://phabricator.ashoat.com/D2363