Improved the instructions for how to install an old editor version

docs/en/shared/install.md

@@ -52,4 +52,6 @@ Installation on Linux
   * macOS: https://d.defold.com/archive/%sha1%/stable/editor2/Defold-x86_64-darwin.dmg
   * Linux: https://d.defold.com/archive/%sha1%/stable/editor2/Defold-x86_64-linux.zip
 
-  Replace `%sha1%` by the editor release hash representing the version in question. The hash of each Defold version can be seen on https://d.defold.com/stable/.
+  Replace `%sha1%` by the editor release hash representing the version in question. The hash of each Defold version can be seen in the links to the released version on the download page at https://d.defold.com/stable/ (make sure to remove the initial # character and only copy the alpha-numeric part):
+
+![download editor](../shared/images/old_version_sha1.png)