Update parse_exceptions.md - correct `json::exception::parse_error`

Fix amount of entries in the json object

Referring to https://github.com/nlohmann/json/blob/develop/doc/examples/parse_error.cpp  and https://json.nlohmann.me/home/exceptions/
(and also based on testing), the catch command should reference `catch (json::parse_error& ex)` and not `catch (json::exception::parse_error& ex)`

After the initial j.push_back() calls there is another j.emplace_back() call that makes the size == 4 not 3.

Better diagnostics

 Conflicts:
	include/nlohmann/detail/input/parser.hpp
	single_include/nlohmann/json.hpp

Fix missing 1.78 in example in README.md

Co-authored-by: Alexander Karzhenkov <karzhenkov@mail.ru>

Add GDB pretty printer

readme: fix tilde character display