Fix typos, update links and conform to Markdown formatting

[tensorush]

Thanks so much for articulating your corporate culture and open-sourcing this playbook! This immediately indicates how thoughtful, transparent and open you are about your processes and operations.

As for this PR, I decided to contribute some superficial, but worthwhile changes, namely:

• Conforming to standard Markdown formatting;
• Fixing minor typos;
• Updating web links.