Deny unknown keys in settings in JSON schema so user gets warnings but settings still parses (#30583)

Closes #ISSUE

Release Notes:

- Improved checking of Zed settings so that unrecognized keys show
warnings while editing them

crates/project/src/project_settings.rs

@@ -36,6 +36,7 @@ use crate::{
 };
 
 #[derive(Debug, Clone, Default, Serialize, Deserialize, JsonSchema)]
+#[schemars(deny_unknown_fields)]
 pub struct ProjectSettings {
     /// Configuration for language servers.
     ///