Use the new burning-envelope banner in the README

Replaces the plain text title with the new banner asset (wordmark,
tagline, and the three platform icons) -- the logo mark is a burning
envelope now, closer to what the product actually does than a bare
flame was.

nccommitted 1 month agoparent 9485d2b671e575e0593692e74da984de4351364f6bdea55Browse files