write documentation requiring React components to have .jsx extension instead of .js

[aqandrew]

Overview

Traditionally, React components may be written in either .js or .jsx files. Our new build tool, Vite, requires that all files containing React components have the .jsx extension. This practice helps to prevent errors during Vite's static analysis of imported files.

Action Items

• decide whether the README is the best place for this documentation to live
• write this documentation, optionally linking to resources below for supporting info

Resources/Instructions

• Why only .jsx extension works with Vite not .js extension in React? vitejs/vite#13715 (comment) quoting Evan You, creator of Vite
• https://stackoverflow.com/a/76726872/6432160