Prettier 2: Electric Boogaloo (#6113)

# Description of Changes
When I added Prettier formatting in #6052, my aim was to use just the
default settings in Prettier. Turns out, Prettier looks _really hard_
for any config files if it's not explicitly given one, which means that
if a developer has some sort of Prettier config file lying around on
their system, Prettier might find it and use it. Also, Prettier changes
its defaults based on stuff in `.editorconfig` without any good way of
disabling that behaviour explicitly in its config file.

To solve both of these issues, I've introduced a `.prettierrc` file
which sets Prettier's defaults explicitly, and then reformatted all our
code _again_ in Prettier's actual default settings. This should achieve
the aim of #6052 and remove the possibility for it breaking on different
dev computers.

frontend/tsconfig.proprietary.vite.json

@@ -7,5 +7,10 @@
       "@core/*": ["src/core/*"]
     }
   },
-  "exclude": ["src/core/**/*.test.ts*", "src/core/**/*.spec.ts*", "src/desktop", "node_modules"]
+  "exclude": [
+    "src/core/**/*.test.ts*",
+    "src/core/**/*.spec.ts*",
+    "src/desktop",
+    "node_modules"
+  ]
 }