[gnome-boxes.wiki] Update source overview

[Felipe Borges <felipeborges src gnome org>]

commit d07ecd3a4643d992b5c600c4d023c3cd6ac93263
Author: Felipe Borges <felipeborges gnome org>
Date:   Fri Jul 30 10:33:06 2021 +0000

    Update source overview

 source-overview.md | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)
---
diff --git a/source-overview.md b/source-overview.md
index 529cd12..73deed8 100644
--- a/source-overview.md
+++ b/source-overview.md
@@ -16,4 +16,12 @@ Our code base is very similar to most of GNOME projects. Although there isn't a
   * org.gnome.Boxes.appdata.xml.in: is our appdata file which specifies how Boxes is presented in Software 
centers such as GNOME Software and Flathub. Check the [AppStream "Metadata" 
documentation](https://www.freedesktop.org/software/appstream/docs/chap-Quickstart.html) for more details.
   * org.gnome.Boxes.desktop.in: See [Desktop Entry 
Specification](https://standards.freedesktop.org/desktop-entry-spec/latest/index.html#introduction).
   * org.gnome.boxes.gschema.xml: These is the Boxes GSettings XML schema. We store in gsettings some 
convinient settings for the application usage such as the last used window size and view type (list view or 
icon view). Our current implementation of Shared Folders uses GSettings to map the host folders to the VM's.
-  * recommended-downloads.xml: Contains a hardcoded list of Osinfo OSes that are promoted in the "Download 
an OS" page. This allows for distributions to pick their own recommended-downloads.
\ No newline at end of file
+  * recommended-downloads.xml: Contains a hardcoded list of Osinfo OSes that are promoted in the "Download 
an OS" page. This allows for distributions to pick their own recommended-downloads.
+* **help/** contains the source for the user documentation available in the *Help* menu option, in the 
gnome-help app, and online at https://help.gnome.org/users/gnome-boxes/stable/index.html
+* **po/** contains the translations.
+* **src/** contains the source code.
+* **subprojects/** contains the source code for libraries bundled within Boxes. These projects are developed 
separately in their own git repositories.
+  * [libovf-glib](https://gitlab.gnome.org/felipeborges/libovf-glib): implements the support for `.OVA` and 
`.OVF` files.
+  * [gtk-frdp](https://gitlab.gnome.org/gnome/gtk-frdp): is a GObject wrapper around the FreeRDP API, which 
provides support for RDP connections in Boxes.
+* **tests/** contains the automated tests.
+* **vapi/** contains Boxes-specific overrides to the Vala language APIs.