language: Accept multiple values in line_comment language knob. (#6713)

This opens up a possibility of supporting multiple comment continuation
flavours in editor, e.g. doc comments for Rust (which we seize as well
in this commit). Only the first `line_comment` value is used for
Editor::ToggleComments

Fixes: https://github.com/zed-industries/zed/issues/6692

Release Notes:
- Added support for doc-comment continuations in Rust language.

crates/zed/src/languages/javascript/config.toml

@@ -1,7 +1,7 @@
 name = "JavaScript"
 path_suffixes = ["js", "jsx", "mjs", "cjs"]
 first_line_pattern = '^#!.*\bnode\b'
-line_comment = "// "
+line_comments = ["// "]
 autoclose_before = ";:.,=}])>"
 brackets = [
     { start = "{", end = "}", close = true, newline = true },
@@ -18,7 +18,7 @@ scope_opt_in_language_servers = ["tailwindcss-language-server"]
 prettier_parser_name = "babel"
 
 [overrides.element]
-line_comment = { remove = true }
+line_comments = { remove = true }
 block_comment = ["{/* ", " */}"]
 
 [overrides.string]