Add __all__ to most modules beginning with 'q', 'r' and 's' (#7364)

stdlib/string.pyi

@@ -7,6 +7,21 @@ if sys.version_info >= (3, 8):
 else:
     from typing import Pattern
 
+__all__ = [
+    "ascii_letters",
+    "ascii_lowercase",
+    "ascii_uppercase",
+    "capwords",
+    "digits",
+    "hexdigits",
+    "octdigits",
+    "printable",
+    "punctuation",
+    "whitespace",
+    "Formatter",
+    "Template",
+]
+
 ascii_letters: str
 ascii_lowercase: str
 ascii_uppercase: str