feat: Add ioveska font as serif fixed font

nixos/modules/gui/default.nix

@@ -54,6 +54,7 @@ in {
         noto-fonts-cjk-serif-static
         noto-fonts
         nerd-fonts.symbols-only
+        iosevka-serif_fixed
       ];
       fontconfig = {
         localConf =

overlays/additions/default.nix

@@ -13,6 +13,7 @@ in
       ./nixvim.nix
       ./doom-emacs.nix
       ./osu-lazer-bin.nix # typochecker: disable-line
+      ./iosevka-serif_fixed.nix
 
       ./pkgsNoCuda.nix
       ./linux-cachyos.nix

overlays/additions/iosevka-serif_fixed.nix

@@ -0,0 +1,45 @@
+{...}: final: _prev: {
+  iosevka-serif_fixed = final.iosevka.override {
+    set = "SerifFixed";
+    privateBuildPlan =
+      #toml
+      ''
+        [buildPlans.IosevkaSerifFixed]
+        family = "Iosevka Serif Fixed"
+        spacing = "fontconfig-mono"
+        serifs = "slab"
+        noCvSs = true
+        exportGlyphNames = false
+
+        [buildPlans.IosevkaSerifFixed.variants.design]
+        zero = "dotted"
+        a = "double-storey-serifless"
+        f = "tailed"
+        i = "serifed-flat-tailed"
+        l = "tailed-serifed"
+        punctuation-dot = "round"
+
+        [buildPlans.IosevkaSerifFixed.weights.Regular]
+        shape = 400
+        menu = 400
+        css = 400
+
+        [buildPlans.IosevkaSerifFixed.weights.Bold]
+        shape = 700
+        menu = 700
+        css = 700
+
+        [buildPlans.IosevkaSerifFixed.slopes.Upright]
+        angle = 0
+        shape = "upright"
+        menu = "upright"
+        css = "normal"
+
+        [buildPlans.IosevkaSerifFixed.slopes.Italic]
+        angle = 9.4
+        shape = "italic"
+        menu = "italic"
+        css = "italic"
+      '';
+  };
+}