settings: accept trailing commas (#2606)

Z-2357

I've found a crate that handles both comments and trailing commas in
JSON. It is a fork of `serde_json`, but it is maintained & up-to-date.
Sadly RawValue seems to not play nicely with it; I've ran into
deserialisation issues around use of RawValue. For this PR I've migrated
to `Value` API.

Obviously this is just a point of discussion, not something I'd merge
straight away. There may be better solutions to this particular problem.

I've also noticed that `serde_json_lenient` does not handle trailing
commas after bindings array. I'm not sure how big of an issue that is.

Release Notes:
- Improved handling of trailing commas in settings files.
[#1322](https://github.com/zed-industries/community/issues/1322)

crates/settings/src/settings_store.rs

@@ -834,11 +834,8 @@ fn to_pretty_json(value: &impl Serialize, indent_size: usize, indent_prefix_len:
 }
 
 pub fn parse_json_with_comments<T: DeserializeOwned>(content: &str) -> Result<T> {
-    Ok(serde_json::from_reader(
-        json_comments::CommentSettings::c_style().strip_comments(content.as_bytes()),
-    )?)
+    Ok(serde_json_lenient::from_str(content)?)
 }
-
 #[cfg(test)]
 mod tests {
     use super::*;