feat: supports multiline usecrate

[sor4chi]

In the current version, a single line with use crate::(.*);$ such as:

use crate::submod1;

is processed correctly. However, in the case of a multi-line use crate statement like:

use crate::{
  submod1,
  submod2
};

it cannot be converted. This is likely because the current implementation only processes single-line use crate statements in here.

rust-sourcebundler/src/bundler.rs

Line 22 in 9f3ec86

static ref USECRATE_RE: Regex = source_line_regex(r" use crate::(?P<submod>.*);$").unwrap();