Use kebab-case for config

book/src/configuration.md

@@ -4,7 +4,7 @@
 
 To disable language server progress report from being displayed in the status bar add this option to your `config.toml`:
 ```toml
-lsp_progress = false
+lsp-progress = false
 ```
 
 ## Theme

helix-term/src/config.rs

@@ -17,6 +17,7 @@ pub struct Config {
 }
 
 #[derive(Serialize, Deserialize)]
+#[serde(rename_all = "kebab-case")]
 struct TomlConfig {
     lsp_progress: Option<bool>,
     keys: Option<HashMap<String, HashMap<String, String>>>,