Add curses.COLORS and curses.COLOR_PAIRS (#3115)

stdlib/2and3/curses/__init__.pyi

@@ -3,7 +3,12 @@ from typing import TypeVar, Callable, Any
 
 _T = TypeVar('_T')
 
+# available after calling `curses.initscr()`
 LINES: int
 COLS: int
 
+# available after calling `curses.start_color()`
+COLORS: int
+COLOR_PAIRS: int
+
 def wrapper(func: Callable[..., _T], *arg: Any, **kwds: Any) -> _T: ...