Various minor updates and fixes

- add ~/.gitconfig
  - update hardcoded home directory links to `~`
  - Switch to using cargo/rustup's auto-generated fish config file instead of handling it in custom.fish

vesktop/settings.json

@@ -1,7 +1,7 @@
 {
-    "minimizeToTray": "on",
+    "minimizeToTray": true,
     "discordBranch": "stable",
-    "arRPC": "on",
+    "arRPC": true,
     "splashColor": "oklab(0.899401 -0.00192499 -0.00481987)",
     "splashBackground": "rgb(0, 7, 32)",
     "spellCheckLanguages": [