xactfetch: Switch to headed Chrome

Earlier this week, `xactfetch` stopped being able to log in to the Chase
website.  After logging in, the website just popped up a message that
said "It looks like this part of our website isn't working right now,"
with a hint that I should try a different browser.  I suspect they have
enhanced their bot detection/scraping resistance, because the error
only occurs when `xactfetch` is run from inside a container.  It happens
every time in that case, but never when I run it on my computer
directly.

After several hours of messing with this, the only way I was able to
get it to work is to use full-blown headed Chromium.  Neither headless
nor headed Firefox works, nor does headless Chromium.  This is a bit
cumbersome, but not really a big deal.  Headed Chromium works fine in
an Xvfb session.

.containerignore

@@ -1,5 +1,6 @@
 *
 !.git
+!entrypoint.sh
 !pinentry-stub.sh
 !pyproject.toml
 !xactfetch.py