Improve receipt spacing and lead with prose

Separate receipt sections and the JSON caveat with blank lines so
shared cards are easier to read. Present prose before code while
preserving benchmark execution, measurements, and receipt metadata.

Refresh the README example and introduce Superterm CE and Pro with
a compact public UI screenshot and a secondary sponsorship note.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>