Improves META6.json documentation

Including `source-type` and clarifying the fact that `source-url` is
compulsory if you want to publish the project in the ecosystem. Closes #2543

doc/Language/modules.pod6

@@ -597,8 +597,9 @@ resources
         └── default-template.mustache
 =end code
 
-The file must then be referenced in C<META6.json> (see below for more on META6.json) so that the distribution path
-can be provided to the program.
+The file must then be referenced in C<META6.json> (see below for more on
+C<META6.json>) so that the distribution path can be provided to the program.
+
 =begin code :lang<javascript>
     {
         "name" : "Vortex::TotalPerspective",
@@ -647,29 +648,26 @@ C<Test>.
 
 =begin item
 
-To document your modules, use L<Perl 6 Pod |/language/pod>
-markup inside your modules. Module documentation is most appreciated and will be
-especially important once  the Perl 6 module directory (or some other site)
-begins rendering Pod docs as HTML for easy browsing. If you have extra docs (in
-addition to the  Pod docs in your module(s)), create a C<doc> directory for
-them. Follow  the same folder structure as the C<lib> directory like so:
+To document your modules, use L<Perl 6 Pod |/language/pod> markup inside them.
+Module documentation is most appreciated and will be especially important once
+the Perl 6 module directory (or some other site) begins rendering Pod docs as
+HTML for easy browsing. If you have extra docs (in addition to the  Pod docs in
+your module(s)), create a C<doc> directory for them. Follow  the same folder
+structure as the C<lib> directory like so:
 
 =begin code :lang<text>
 doc
 └── Vortex
     └── TotalPerspective.pod6
 =end code
-
-=end item
-
-=item
-Note, described above is a minimal project directory. If your project
+N<Note, described above is a minimal project directory. If your project
 contains scripts that you'd like distributed along with your module(s),
 put them in a C<bin> directory. If you'd like a graphical logo to
 appear next to your module at the module directory, create a
 C<logotype> directory and put into it a C<logo_32x32.png> file. At some
 point, you might also consider adding C<CONTRIBUTORS>, C<NEWS>,
-C<TODO>, or other files.
+C<TODO>, or other files.>
+=end item
 
 =begin item
 
@@ -742,7 +740,10 @@ are used in those phases of the of installation. The last two are optional, but
 convenient.
 
 Finally, C<source-url> indicates the URL of the repository where the module is
-developed.
+developed; this is one of the compulsory modules if you are going to publish it
+in the module ecosystem. It is convenient to also provide the C<source-type>
+field, which indicates the kind of source control system, generally C<git>,
+which can be used to download the module.
 
 The L<Test::META module | https://github.com/jonathanstowe/Test-META/>
 can help you check the correctness of the META6.json file.
@@ -880,4 +881,4 @@ L<https://github.com/perl6/toolchain-bikeshed>.
 
 =end pod
 
-# vim: expandtab softtabstop=4 shiftwidth=4 ft=perl6
+# vim: expandtab softtabstop=4 shiftwidth=4 ft=perl6