[shipit-ascii-art] Modernize the ASCII Art extension.
Review Request #11088 — Created July 20, 2020 and submitted
This change modernizes the Ship It! ASCII Art extension and dramatically
simplifies the codebase by consolidating everything into the extension
file, while deleting unused code. Most notably, it switches to using
SignalHook to connect the signal handler, which will behave correctly
when deactivating the extension.
Activated the extension and verified the results.