🚀 Feature: Add an "explainer" page tailored to technical leaders

[JoshuaKGoldberg]

Bug Report Checklist

• I have tried restarting my IDE and the issue persists.
• I have pulled the latest main branch of the repository.
• I have searched for related issues and found none that matched my issue.

Overview

We'd like to have a page specifically made to be sent to folks who lead technical departments (e.g. CTOs), to explain why they should approve developer time working on open source:

1. 🚀 Feature: Add an "explainer" page for what open source is for software developers #21
2. 🚀 Feature: Add an "explainer" page for why contributing to open source benefits a company #23
3. 🚀 Feature: Add a guide page explaining how to contribute to open source as a company #24

Additional Info

Per #20, we'll eventually have a full design for the site & menus. But for now this page can live on its own.

This site is built on Next.js. You can create a new page by adding a .md file under src/pages. See https://nextjs.org/docs/basic-features/pages.