[CaR Grant] Document Rational.base-repeating with no args

Spec: Raku/roast@7263105372
Rakudo impl: since before the Christmas

Author: zoffixznet

doc/Type/Rational.pod6

@@ -93,7 +93,7 @@ numerator and denominator coprime.
 
 =head2 method base-repeating
 
-    method base-repeating(Rational:D: Int:D() $base)
+    method base-repeating(Rational:D: Int:D() $base = 10)
 
 Returns a list of two strings that, when concatenated, represent the number in
 base C<$base>. The second element is the one that repeats. For example:
@@ -112,6 +112,8 @@ If no repetition occurs, the second string is empty:
 The precision for determining the repeating group is limited to 1000
 characters, above that, the second string is C<???>.
 
+C<$base> defaults to C<10>.
+
 =end pod
 
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