[fractal/add_security_considerations] docs: Explain how credentials are stored

[Julian Sparber <jsparber src gnome org>]

commit 3c4223ee33e365a9c08e140a603054fcf207ad12
Author: Julian Sparber <julian sparber net>
Date:   Sat Sep 10 11:00:40 2022 +0000

    docs: Explain how credentials are stored

 README.md | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/README.md b/README.md
index 72307500c..134eb7a80 100644
--- a/README.md
+++ b/README.md
@@ -100,6 +100,10 @@ Fractal is translated by the GNOME translation team on [Damned lies](https://l10
 
 Find your language in the list on [the Fractal module page on Damned 
lies](https://l10n.gnome.org/module/fractal/).
 
+### Security considerations
+
+Fractal uses [SecretService](http://standards.freedesktop.org/secret-service/) to store the access token and 
the passphrase to access the local cache. Generally, when Fractal is used with GNOME. The information stored 
via the SecretService is stored in the [GNOME Keyring](https://wiki.gnome.org/Projects/GnomeKeyring), which 
on the other hand, by default, uses the users password to access the stored information.
+
 ## Frequently Asked Questions
 
 * Does Fractal have encryption support? Will it ever?