Support for the CH32V003 chip

[aykevl]

Work in progress.

To try, you need to make the lib/cmsis-svd/data/WCH-Community/ directory and download https://github.com/ch32-rs/ch32-rs/blob/main/svd/vendor/CH32V003xx.svd into that directory.

Also, you need to install probe-rs.

Not nearly finished. I'd like to get at least the timer working before marking this PR as ready.

[aykevl]

We might need to add a new way of generating register files: ch32-rs/ch32-rs#21
Basically it seems like development on register files now happens here: https://github.com/ch32-rs/ch32-data, but unfortunately they store the files in a custom YAML based format (not in standard SVD format).