Delete the progress log

That information belongs in the commit messages. I'll take care in the
future, for now it's lost (not really, you can still read it).

progress_log.md

@@ -1,17 +0,0 @@
-# Progress log
-
-- (4/9/2023) Finished 5 chapters out of 7, basic text editing is fully
-possible. It has fun been working on this, but semester is starting now and I
-might not get to work on this a lot anymore. It might have lots of bugs, and
-there's lots of things I don't like, there are TODOs everywhere. So many leaky
-abstractions, near the end I started blindly following the tutorial and didn't
-stop to think how it fits with the abstractions I have defined, but I might fix
-it all one of these days...
-
-- (9/9/2023) Didn't implement any new features, but refactored heavily. All the
-previous features should be working unless I introduced a bug. But I like the
-abstractions better now, and I cleaned up most of TODOs. This was painful to
-get right and I contemplated quitting, but proud of myself. I find it very
-interesting that the total of amount of code barely changed, it actually
-decreased as measured by tokei. It increased slightly in the header files and
-decreased in the source files, yet it was a lot of work.