wezterm: move os specific stuff into a single function call

dot_config/wezterm/wezterm.lua

@@ -8,6 +8,18 @@ local tab_fg = '#ebdbb2'
 local tab_bg = '#504945'
 local tab_bg_active = '#282828'
 
+-- os specific stuff
+local myos = fn.set_by_os{
+    Darwin = {
+        font_size = 14,
+        window_decorations = "TITLE | RESIZE"
+    },
+    others = {
+        font_size = 10,
+        window_decorations = "RESIZE"
+    }
+}
+
 -- misc
 local cfg = wt.config_builder()
 cfg.leader = kb.leader
@@ -20,14 +32,10 @@ cfg.cursor_blink_rate = 0
 cfg.bold_brightens_ansi_colors = false
 cfg.font = wt.font('Cascadia Mono PL')
 cfg.harfbuzz_features = {"ss01", "ss19", "ss20"}
-cfg.font_size = fn.set_by_os{
-    Darwin = 14,
-    others = 10
-}
-
+cfg.font_size = myos.font_size
 -- visuals
 cfg.native_macos_fullscreen_mode = false
-cfg.window_decorations = 'RESIZE'
+cfg.window_decorations = myos.window_decorations
 cfg.xcursor_theme = 'Adwaita'
 cfg.use_fancy_tab_bar = false
 cfg.hide_tab_bar_if_only_one_tab = false