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/Cargo.toml

@@ -21,7 +21,7 @@ util = { path = "../util" }
 
 anyhow.workspace = true
 futures.workspace = true
-json_comments = "0.2"
+serde_json_lenient = {version = "0.1", features = ["preserve_order", "raw_value"]}
 lazy_static.workspace = true
 postage.workspace = true
 rust-embed.workspace = true
@@ -37,6 +37,6 @@ tree-sitter-json = "*"
 [dev-dependencies]
 gpui = { path = "../gpui", features = ["test-support"] }
 fs = { path = "../fs", features = ["test-support"] }
-
+indoc.workspace = true
 pretty_assertions = "1.3.0"
 unindent.workspace = true