config(fish): add fish completions for cli tools

dot_config/fish/conf.d/50-terminal-title.fish

@@ -0,0 +1,8 @@
+# Set the tmux/screen window name from $PWD (the ESC-k sequence).
+# fish_title() handles the regular terminal title; this targets multiplexers.
+status is-interactive; or return
+
+function terminal_title --on-variable PWD
+    printf '\033k%s\033\\' (prompt_pwd)
+end
+terminal_title