docs: fully write the readme

Author: YoRyan

README.md

@@ -1,2 +1,53 @@
-# railroads-cli
-Companion configuration and mod installing tool for Sid Meier's Railroads!
+# railroadscli
+
+railroadscli is a companion modding tool for *Sid Meier's Railroads!* You can use it to make the game more stable (by [enabling](https://steamcommunity.com/sharedfiles/filedetails/?id=1349679487) LAA), turn on secret features like the map editor, play online over the [OpenSpy](https://openspy.net) network, and install custom [maps](https://smr-maps.trinancrat.me/) from the [Internet Archive](https://archive.org/details/sid-meiers-railroads-custom-maps-collection) and other repositories of [SAM](https://smrsimple.com/2009/06/what-is-a-sam/) (stand-alone map) content. It's heavily inspired by the [Definitive SMR Launcher](https://github.com/ageekhere/Definitive-SMR-Launcher), but in close comparison, railroadscli is faster and lighter, doesn't require admin rights, and, of course, supports Linux and SteamOS.
+
+When run without arguments (i.e., double-clicked on in Windows Explorer) railroadscli applies all desired options from a same-directory TOML file named `railroadscli.toml`. The full format of this file is as follows. It is easy to share with friends if you want to play online with the same content.
+
+```toml
+# Override auto-detection of the user data directory
+# Default: <Documents>\My Games\Sid Meier's Railroads
+game_data_path = "C:\\Users\\Sid\\Documents\\My Games\\Sid Meier's Railroads"
+
+# Override auto-detection of the game install directory
+# Default: path to app ID 7600 in your Steam library
+game_install_path = "C:\\Program Files (x86)\\Steam\\steamapps\\common\\Sid Meier's Railroads"
+
+# Configure Settings.ini for maximum graphical quality and anti-aliasing
+# Default: true
+best_graphics = true
+
+# Skip or play the intro movies
+# Default: true
+skip_opening = true
+
+# Enable or disable the terrain editor
+# Default: true
+enable_editor = true
+
+# Set the LAA flag to allow the game to exceed 2GB of virtual memory
+# Default: true
+laa_aware = true
+
+# Set the GameSpy master server domain (must be 11 characters long)
+# Default: openspy.net (the only known working network)
+gamespy_server = "openspy.net"
+
+# Prompt before deleting the contents of the UserMaps and CustomAssets directories
+# Default: true
+warn_on_delete = true
+
+# Download and extract an archive to the UserMaps directory, overwriting existing contents
+# Default: do nothing
+usermaps_from = "https://archive.org/download/sid-meiers-railroads-custom-maps-collection/A_Tycoon's_Tale_v1_00.7z"
+
+# Download and extract an archive to the CustomAssets directory, overwriting existing contents
+# Default: do nothing
+#customassets_from = ""
+
+# When in automatic (no arguments provided) mode, launch the game after applying this configuration
+# Default: true
+autolaunch = true
+```
+
+You can obtain a copy of railroadscli from the GitHub releases [page](https://github.com/YoRyan/railroads-cli/releases). To see all available command-line options, refer to `railroadscli --help` and `railroadscli config --help`.