Adds Boolean literals, closes #2552

doc/Language/syntax.pod6

@@ -553,7 +553,7 @@ is a representation of a constant value in source code. Perl 6 has literals
 for several built-in types, like L<strings|/type/Str>, several numeric types,
 L<pairs|/type/Pair> and more.
 
-
+X<|String (literals)>
 =head3 String literals
 
 String literals are surrounded by quotes:
@@ -573,6 +573,7 @@ X<|0b (radix form)>
 X<|0d (radix form)>
 X<|0o (radix form)>
 X<|0x (radix form)>
+X<|Number (literals)>
 =head3 Number literals
 
 Number literals are generally specified in base ten, unless a prefix
@@ -646,6 +647,7 @@ a real and an imaginary number:
     6.123e5i    # note that this is 6.123e5 * i, not 6.123 * 10 ** (5i)
     =end code
 
+X<|Pairs (literals)>
 =head3 Pair literals
 
 L<Pairs|/type/Pair> are made of a key and a value, and there are two
@@ -697,6 +699,12 @@ Long forms with explicit values:
 :thing{a => 'b'}            # same as  thing => { a => 'b' }
 =end code
 
+X<|Boolean (literals)>
+=head3 Boolean literals
+
+C<True> and C<False> are Boolean literals; they will always have initial capital
+letter.
+
 =head3 Array literals
 
 A pair of square brackets can surround an expression to form an itemized