Hardcode default config, and document how config works

.config/config.json5

@@ -3,15 +3,7 @@
     {
       "user_id": "@alice:example.org",
       "password": "hunter2",
+      // Optional: "device_name": "ratatrix on <hostname>",
     },
   ],
-  "keybindings": {
-    "Home": {
-      "<Ctrl-d>": "/quit",
-      "<Ctrl-c>": "/quit",
-      "<Ctrl-z>": "/suspend",
-      "<Alt-left>": "/previous",
-      "<Alt-right>": "/next",
-    },
-  }
 }

.config/config.toml

@@ -0,0 +1,4 @@
+[[accounts]]
+user_id = "@alice:example.com"
+password = "hunter2"
+# Optional: device_name = "ratatrix on <hostname>"

README.md

@@ -1,2 +1,18 @@
 # ratatrix
 
+## Setup
+
+1. Create an account on [any Matrix homeserver](https://servers.joinmatrix.org/)
+2. Install Rust
+3. Copy `.config/config.toml` or `.config/config.json5` to `~/.config/ratatrix/`
+   and fill the placeholders with your credentials
+4. `cargo run`
+
+## Configuration
+
+Ratatrix supports multiple configuration format: TOML, JSON/JSON5, YAML, and INI,
+you may choose whichever you prefer. If you don't have a preference, pick TOML.
+Example configurations for TOML and JSON5 are provided in `.config`.
+
+Default values for all settings, and their documentation, can be found in
+`src/default_config.toml`.

src/config.rs

@@ -13,6 +13,8 @@ use serde_json::Value as JsonValue;
 
 use crate::{action::Action, mode::Mode};
 
+const DEFAULT_CONFIG: &str = include_str!("default_config.toml");
+
 #[derive(Clone, Debug, Deserialize, Default)]
 pub struct AppConfig {
   #[serde(default)]
@@ -55,7 +57,11 @@ impl Config {
     let config_dir = crate::utils::get_config_dir();
     let mut builder = config::Config::builder()
       .set_default("_data_dir", data_dir.to_str().unwrap())?
-      .set_default("_config_dir", config_dir.to_str().unwrap())?;
+      .set_default("_config_dir", config_dir.to_str().unwrap())?
+      .add_source(config::File::from_str(
+        DEFAULT_CONFIG,
+        config::FileFormat::Toml,
+      ));
 
     let config_files = [
       ("config.json5", config::FileFormat::Json5),

src/default_config.toml

@@ -0,0 +1,7 @@
+# Key bindings in the main "Home" mode
+[keybindings.Home]
+"<Ctrl-d>" = "/quit"
+"<Ctrl-c>" = "/quit"
+"<Ctrl-z>" = "/suspend"
+"<Alt-left>" = "/previous"
+"<Alt-right>" = "/next"