Problem: Docs about how to obtain backtraces on Linux is not very
beginner-friendly; some users used to have difficulties in getting
stacktrace against Nvim crash.
For instance, the `core` dump file might not appear in the current
directory on Ubuntu systems with apport, and the current docs do not
fully cover such cases.
Solution: Add more hints about where core dump files can be found. For
example, on Ubuntu where apport is managing core dump files, users would
want to find them in `/var/lib/apport/coredump`.
56b7a18995
