Add Best Practices for Client implementors

[tadasant]

i.e. land #36

[tadasant]

Ideas from meeting:

• For the in-client popup, maybe we should show the chain of github.com's ai-catalog referenced api.githubcopilot.com, and the latter domain owns what you are installing
• Create a browser extension that can e.g. discover MCP servers on a website and provide a popup/button/modal for one-click installs into e.g. VS Code as a product of your (human) website browsing
• Make sure you dedupe e.g. "you've already installed XYZ server" and don't overload with too many options. Provide affordances for "don't ask me again", etc