README: Add e2ee explanation, config note

next to TrayIcon one. New note in config tells you why E2EE might be
missing.

README.md

@@ -59,6 +59,8 @@ jfa-go is a user management app for [Jellyfin](https://github.com/jellyfin/jelly
 
 **Note**: `TrayIcon` builds include a tray icon to start/stop/restart, and an option to automatically start when you log-in to your computer. For Linux users, these builds depend on the `libappindicator3-1`/`libappindicator-gtk3`/`libappindicator` package for Debian/Ubuntu, Fedora, and Alpine respectively.
 
+`MatrixE2EE` builds (and Linux `TrayIcon` builds) include support for end-to-end encryption for the Matrix bots, but require the `libolm(-dev)` dependency. `.deb/.rpm/.apk` packages list this dependency, and docker images include it.
+
 ##### [Docker](https://hub.docker.com/r/hrfee/jfa-go)
 ```sh
 docker create \
@@ -88,7 +90,7 @@ sudo apt-get update
 # For servers
 sudo apt-get install jfa-go
 # ------
-# For desktops/servers with GUI (has dependencies)
+# For desktops/servers with GUI (may pull in lots of dependencies)
 sudo apt-get install jfa-go-tray
 # ------
 ```

config/config-base.json

@@ -1311,6 +1311,14 @@
                     "type": "bool",
                     "value": true,
                     "description": "Enable end-to-end encryption for messages."
+                },
+                "e2ee_note": {
+                    "name": "End-to-end encryption:",
+                    "type": "note",
+                    "value": "",
+                    "depends_true": "enabled",
+                    "required": "false",
+                    "description": "If the setting is not visible to you, your jfa-go version does not include the feature. See the wiki for more information."
                 }
             }
         },