EVI Web Example Polishing

[norman-codes]

Minor details on the EVI web examples using TypeScript, the NextJS Pages Router, and the NextJS App Router were changed.

• An example .env file (.env.example) was added to the TypeScript example and references to it (and using a .env file for authentication) were updated in the corresponding README. Note that it was attempted to have the placeholder file be named .env directly, but after researching best practices for environment variable files in GitHub repositories, I decided to use .env.example instead.
• The name of the export function for the Messages.tsx components in the EVI NextJS App Router and Pages Router example repositories is changed to match the component's name.