fix: Copyedits

[sarahmonster]

Three small changes:

• Update the SVG code for the MacRumors badge so it uses the correct typeface on machines that aren't mine. (Whoops.)
• Copyedit the privacy policy a wee bit to flesh out some details about the data we collect. (And add emoji.)
• Copyedit the under the hood page to link back to Matt's blog post, and improve readability.