Improve README
Improve README

Improve clarity, grammar, consistency, punctuation, and formatting.

PR #3177 <https://github.com/Genymobile/scrcpy/pull/3177>

Signed-off-by: Romain Vimont <a1e17a20e93e5da710685444df3ad038ac66e2c9@rom1v.com>

Genymobile/scrcpy,Genymobile/scrcpy,Genymobile/scrcpy