Start to document literals

lib/Language/syntax.pod

@@ -194,15 +194,25 @@ variables:
     say Meta.type-name;     # Meta
     #   ^^^^ type name
 
-=begin comment
 
 =head2 Literals
 
-TODO
+A L<literal|https://en.wikipedia.org/wiki/Literal_%28computer_programming%29>
+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.
+
 
 =head3 String literals
 
-TODO: link to quotes
+String literals are surrounded by quotes:
+
+    say 'a string literal';
+    say "a string literal\nthat interprets escape sequences";
+
+See L<quoting|/language/quoting> for many more options.
+
+=begin comment
 
 =head3 Number literals