macOS: add menu items for new_window and close_window

[Luflosi]

As promised in #3647.
Please double-check that I made the changes in exactly the right places, not in too few places and not in too many. I basically just searched the code base for an already existing shortcut and then replicated the appropriate looking code for the new shortcuts.
Should I sort the shortcuts in the code into a particular order or just append to the end like I did now?
I successfully tested this change.

[kovidgoyal]

The changes look correct but i suggest adding a shortcut for reset terminal as well.

[Luflosi]

I don't use reset_terminal. What exact action should occur? clear_terminal reset active?

[kovidgoyal]

yes.

[Luflosi]

I'll try to do that in a future PR as it is not quite as simple as the other two options. I got everything working except for binding to the correct keyboard shortcut. If I have

#:     # Reset the terminal
map kitty_mod+f9 clear_terminal reset active
#:     # Clear the terminal screen by erasing all contents
map kitty_mod+f10 clear_terminal clear active
#:     # Clear the terminal scrollback by erasing it
map kitty_mod+f11 clear_terminal scrollback active
#:     # Scroll the contents of the screen into the scrollback
map kitty_mod+f12 clear_terminal scroll active

in my kitty.conf, the keyboard shortcut will be cmd+F12 instead of cmd+F9. I'll try to fix that in the near future and then make a new PR just for that.