docs: Add a tutorial for pystack core

[PistachioCannoli]

The tutorial walks users through a core dump configuration, then uses a python script to invoke a dump with stdlib SIGABRT, and then utilizes pystack to trace the error.

*Issue number of the reported bug or feature request: #53 *

Describe your changes
Wrote a tutorial page which guides users through a stack trace with pystack's core subcommand. The tutorial starts by introducing the concept, then configures the core dump settings such as size and output location. Afterwards, it uses a test script written which follows a series of asserts, if an assert is thrown, stdlib abort is called to interrupt the program, causing a core dump. Finally, the tutorial uses the core subcommand to trace the specific python stack then uses the --native flag to show the native C frames to assess the error.

Testing performed
Tested in an environment which copied the documentation structure of memray, but I reverted all memray dependencies prior to committing my changes.