Add ability to specify decimal separator in Polars SQL read_csv table function.

[jqnatividad]

Description

Now that #15774 has been merged, it'd be great if Polars SQL users have to ability to specify their desired decimal operator with the Polars SQL read_csv table function.

Currently, it only supports one parameter - the CSV filepath.

polars/crates/polars-sql/src/table_functions.rs

Lines 80 to 88 in 4a870cc

	#[cfg(feature = "csv")]
	fn read_csv(&self, args: &[FunctionArg]) -> PolarsResult<(String, LazyFrame)> {
	polars_ensure!(!args.is_empty(), ComputeError: "read_csv expected a path");
	use polars_lazy::frame::LazyFileListReader;
	let path = self.get_file_path_from_arg(&args[0])?;
	let lf = LazyCsvReader::new(&path).finish()?;
	Ok((path, lf))
	}