Use sentence casing in JS nutshell page

doc/Language/js-nutshell.pod6

@@ -11,7 +11,7 @@ well as major differences in syntax and features.
 This is not a tutorial for learning Perl 6; this is a reference for users who
 are already at an intermediate to advanced skill level with Node.js.
 
-=head1 Basic Syntax
+=head1 Basic syntax
 
 =head2 "Hello, world!"
 
@@ -327,7 +327,7 @@ say 1 +^ 1; # 0
 say +^1;    # -2
 =end code
 
-=head3 Custom Operators and Operator Overloading
+=head3 Custom operators and operator overloading
 
 Node.js does not allow operator overloading without having to use a Makefile or
 build Node.js with a custom version of V8. Perl 6 allows custom operators and
@@ -367,7 +367,7 @@ say ++$foo; # 0
 
 # TBD
 
-=head2 Control Flow
+=head2 Control flow
 
 =comment TODO
 
@@ -385,25 +385,25 @@ say ++$foo; # 0
 
 # TBD
 
-=head1 Object-Oriented Programming
+=head1 Object-oriented programming
 
 =comment TODO
 
 # TBD
 
-=head1 The Networking API
+=head1 The networking API
 
 =comment TODO
 
 # TBD
 
-=head1 The Filesystem API
+=head1 The filesystem API
 
 =comment TODO
 
 # TBD
 
-=head1 Modules and Packages
+=head1 Modules and packages
 
 =comment TODO