Update json5 crate dependency from 0.4.1 to 1.3.1

[notpeter]

This updates the JSON5 dependency from v0.4.1 (2021-09-21) to v1.3.1 (2026-02-27).

If you look at the diff of 0.4.1...1.3.1 you can see v1.0.0 was a clean rewrite which switched licenses (ISC to MIT) and switched from a PEST.rs generated backend to a hand-written one.

This results in a smaller download (net -1.7MB when dependencies included) and a slightly faster build (1-3% when building config-rs with default features on my M5 Pro Macbook).

According to the author, performance is ~20x better:

google/serde_json5 was a fork of the Pest version of serde_json5

[epage]

See

  error[E0658]: `let` expressions in this position are unstable
     --> /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/json5-1.3.1/src/de.rs:271:15
      |
  271 |         while let Some((o, c)) = self.peek()
      |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      |
      = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information

I had previously looked at this in #741.