Add a FAQ section to the `README.md`

[mikenikles]

Questions that need answers:

• How is OpenVSCode Server different from VS Code?
• How is OpenVSCode Server different from Gitpod?
• How is OpenVSCode Server different from the Remote SSH VS Code extension?
• How is OpenVSCode Server different from code-server?
• How do I create a Node / Java / C / etc environment?
• How do I authenticate with GitHub?
• How do I protect my instance of OpenVSCode Server?
• Is it safe to run as root?