add writeupfor july 2023 (#202)

* add writeupfor july 2023

* Update _hacks/39.md

Co-authored-by: Hugh Rawlinson <hughrawlinson@users.noreply.github.com>

* Update _hacks/39.md

Co-authored-by: Hugh Rawlinson <hughrawlinson@users.noreply.github.com>

---------

Co-authored-by: Hugh Rawlinson <hughrawlinson@users.noreply.github.com>

Author: lpmi-13

_hacks/39.md

@@ -1,5 +1,20 @@
 ---
 hack_number: 39
 date: 2023-07-29
-upcoming: true
 ---
+
+Oh, those sweet summer duldrums...when half of us are following along lackadaisically with apparent evidence of UFOs, and the other half are trying to reproduce an experiment to basically revolutionise the flow of energy itself...
+
+..but then we all went on holiday, lol.
+
+## Things people did before/after/during said holiday
+
+- **Ryan** hacked on, in his own words, "synchronous-feeling background jobs", and also guitar amp AI stuff. There is no evidence of how it went.
+
+- **Joe** cheated and did work, but it was on curriculum for a Godot course, so we'll allow it.
+
+- **Tom** Tried to improve the software that drives his own custom addressable RGB LED matrices using fancy data structures called interval trees - and he learned a lot about them!
+
+- **Hugh** worked on making his keyboard layout for his silly 3d printed keyboard configurable in web browsers that aren't super concerned about user privacy, which is useful for typists who are particularly concerned about not having to compile c every time they want to move a key (and also very helpfully wrote his own writeup in the discord chat, which was the most helpful thing anybody did all hackday).
+
+- **Adam** wasn't able to join, but at some point submitted the third PR in the attempt to fix the automation to update the frontpage with the next hackday...and it finally worked. So he might just take the rest of the year off.