[gimp-help] Update README with a little extra info about the Inno Setup language files.

[Jacob Boerema <jboerema src gnome org>]

commit 8b1177bd400a70e832daada931a7259cf87780ba
Author: Jacob Boerema <jgboerema gmail com>
Date:   Mon Mar 28 19:24:08 2022 -0400

    Update README with a little extra info about the Inno Setup language files.

 README.md | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/README.md b/README.md
index 2091bc046..a50116d3f 100644
--- a/README.md
+++ b/README.md
@@ -341,9 +341,12 @@ of languages needs to be updated in the following files:
       the build job because we don't want time-outs.
   - 
[build/windows/installer/installer-gimp-help-msys2.sh](build/windows/installer/installer-gimp-help-msys2.sh)
     - Check if the language is part of the official languages installed
-      together with Inno Setup.
-    - If not, check if there is an unofficial translation.
+      together with Inno Setup. An up-to-date list can be found at
+      [github](https://github.com/jrsoftware/issrc/tree/main/Files/Languages).
+    - If not, check if there is an unofficial translation,
+      [here](https://github.com/jrsoftware/issrc/tree/main/Files/Languages/Unofficial).
     - If there is, then add it to the download_lang commands.
+    - If no translation is available `Default.isl` can be used.
   - [build/windows/installer/gimp-help.iss](build/windows/installer/gimp-help.iss)
     - Add a if LANG test and define LANGFILE for you language.
   - [TRANSLATING](.TRANSLATING)