README: fix typo
README: fix typo

Change-Id: Id744d5f994bed6522f3be7d6b90e6b78bd8da587

webmproject/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,webmproject/libwebp,PKRoma/libwebp