Add yEd graph editor mention to the software list appendix

Author: shorodilov

src/appx/software_list.rst

@@ -6,6 +6,21 @@
 Software List
 =============
 
+yEd - Graph editor
+------------------
+
+yEd is a powerful desktop application that can be used to quickly and
+effectively generate high-quality diagrams. Create diagrams manually, or
+import your external data for analysis. Our automatic layout algorithms
+arrange even large data sets with just the press of a button.
+yEd is freely available and runs on all major platforms:
+Windows, Unix/Linux, and macOS.
+
+https://www.yworks.com/products/yed
+
+`Online live version <https://www.yworks.com/products/yed-live>`_
+is also available.
+
 7zip
 ----
 
@@ -78,8 +93,6 @@ reputation for reliability, feature robustness, and performance.
 
 https://www.postgresql.org/
 
-.. _psqlcygwin-pkg:
-
 psql [#cygwin]_
 ---------------