update fish config

dot_config/fish/config.fish

@@ -0,0 +1,19 @@
+# disable fish greeting
+set fish_greeting
+
+# nix
+if command -v nix >/dev/null
+    fish_add_path ~/.nix-profile/bin
+end
+
+# direnv
+if command -v direnv >/dev/null
+    direnv hook fish | source
+    set -g direnv_fish_mode eval_on_arrow 
+end
+
+# starship
+if command -v starship >/dev/null
+    source (starship init fish --print-full-init | psub)
+end
+