put steam example image on readme

Program.cs

@@ -470,7 +470,7 @@ static async Task<Process> LaunchGame(string filename, string? exchange, EpicAcc
             string legendaryInstalledPath = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData) +
                 "/heroic/legendaryConfig/legendary/installed.json";
 
-            Dictionary<string, LegendaryManifestEntry> manifests;
+            Dictionary<string, LegendaryManifestEntry>? manifests;
             try
             {
                 string manifeststring = File.ReadAllText(legendaryInstalledPath);

README.md

@@ -1,28 +1,52 @@
 # EricLauncher
 
-A very bare-bones launcher for Epic Games Store games **that have already been installed via the official launcher**. Designed for Windows and written in C# using .NET 8.0.
+A very bare-bones launcher for Epic Games Store games **that have already been
+installed via the official launcher**. Designed for Windows and written in C#
+using .NET 8.0.
 
-This application was written for personal usage and isn't 100% user oriented. If you're looking for something more stable, tested, reliable, featureful and/or cross-platform, check out [Legendary (CLI)](https://github.com/derrod/legendary) or [Heroic Games Launcher (GUI)](https://github.com/Heroic-Games-Launcher/HeroicGamesLauncher).
+This application was written for personal usage and isn't 100% user oriented.
+If you're looking for something more stable, tested, reliable, featureful
+and/or cross-platform, check out [Legendary (CLI)](https://github.com/derrod/legendary)
+or [Heroic Games Launcher (GUI)](https://github.com/Heroic-Games-Launcher/HeroicGamesLauncher).
 
 **This does not handle cloud save games, you may lose save data!**
 
-**This is provided without any warranty, I am not responsible for your account getting banned, your save data being lost, your hard drive exploding, getting sniped at 2nd in a Battle Royale, or thermonuclear war.**
+**This is provided without any warranty, I am not responsible for your account
+getting banned, your save data being lost, your hard drive exploding, getting
+sniped at 2nd in a Battle Royale, or thermonuclear war.**
 
 ## Features
 
 - Logging in to Epic Games accounts.
-- Multi-account support. (specify an `--accountId` or `--account` at the command line.)
-- Checking for Fortnite updates. (if an update is available, the game will not launch.)
+- Multi-account support. (specify an `--accountId` or `--account` at the command
+  line.)
+- Checking for Fortnite updates. (if an update is available, the game will not
+  launch.)
 - Windows and macOS support, as well as providing launch args on Linux.
-- Support for at least some games. (tested with Fortnite, Borderlands 3, Death Stranding and FUSER.)
+- Support for at least some games. (tested with Fortnite, Borderlands 3, Death
+  Stranding and FUSER.)
     - Including games that require ownership tokens. (in theory)
 - Offline game launching. (only works on some games)
 
 ## Usage
 
-This is designed to be run from the command line, but you can drag and drop a game's primary executable onto it and it should work.
+This is designed to be run from the command line, but you can drag and drop a
+game's primary executable onto it and it should work.
 
-Alternatively you could make a batch file or shortcut, or create a shortcut in a launcher such as Steam - pointing to EricLauncher, with the game you want to launch as the launch arguments
+**For Fortnite, the game's primary executable is always FortniteLauncher.exe**
+
+Alternatively you could make a batch file or shortcut, or create a shortcut in
+a launcher such as Steam - pointing to EricLauncher, with the game you want to
+launch as the launch arguments
+
+### Steam Usage
+
+Add EricLauncher.exe as a non-Steam shortcut, then set the launch arguments on
+the shortcut to be the path to your game's executable.
+
+![Steam Properties window for a game named 'Fortnite', which shows the 'Target' as being 'EricLauncher.exe' and 'Launch Options' as being 'FortniteLauncher.exe'](readme_assets/steam_example.png)
+
+### Command Line Usage
 
 ```
 Usage: EricLauncher.exe [game executable path or verb] (options) (game arguments)
@@ -42,11 +66,17 @@ Verbs:
   logout    - Logs out of Epic Games.
 ```
 
-The account ID parameter is only required if you are using multiple accounts. Omitting this value will use (or save) a default account.
+The account ID parameter is only required if you are using multiple accounts.
+Omitting this value will use (or save) a default account.
+
+For best results, make sure the game has been launched at least once by the
+official Epic Games Launcher, and the provided executable path is the same one
+that gets launched by the official launcher.
 
-For best results, make sure the game has been launched at least once by the official Epic Games Launcher, and the provided executable path is the same one that gets launched by the official launcher. (Heroic support is preliminary but should work on Windows.)
+(Heroic support is preliminary but should work on Windows, use `--heroic`)
 
-Epic Games session files are stored in `%localappdata%\EricLauncher`. You can log out of EricLauncher by running `EricLauncher.exe logout`.
+Epic Games session files are stored in `%localappdata%\EricLauncher`. You can
+log out of EricLauncher by running `EricLauncher.exe logout`.
 
 ## TODO