Get <1.70 Working Again

[michaelciraci]

Currently, exrs (and as a result, image) does not compile as a dependency for rust <1.70 due to a breaking change with half:

cargo +1.69 test   
    Updating crates.io index
error: package `half v2.3.1` cannot be built because it requires rustc 1.70 or newer, while the currently active rustc version is 1.69.0
Either upgrade to rustc 1.70 or newer, or use
cargo update -p half@2.3.1 --precise ver
where `ver` is the latest version of `half` supporting rustc 1.69.0

The breaking change in half is documented here

This merge requests bounds half to allow compilation again with rust <1.70.

In addition, Cargo.lock should be added to .gitignore since this is a package and not library: https://doc.rust-lang.org/cargo/faq.html#why-do-binaries-have-cargolock-in-version-control-but-not-libraries

[johannesvollmer]

done :) https://github.com/johannesvollmer/exrs/releases/tag/v1.6.5

as a minor release, this should "automatically" replace any previous versions (if you update your versions in the Cargo.lock)