Two bugs of 3.12.0 are fixed on develop without a note on the pages.
With JSON_DIAGNOSTIC_POSITIONS, start_pos() of a string that contains
escape sequences was too large; the position is now that of the opening
quote. A parse error for an unexpected number that is followed by a line
feed reported column 0 (for "1 2" and a line feed, line 1, column 0); for
"1", line feed, "2", line feed it now reports line 2, column 1.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>