Add support for pre-release and metadata

[gyscos]

Also updates dependencies to not crash.

Fixes #8

[wraithan]

The metadata feature is welcome. If I don't hear back from you before next weekend, I'll pull apart the PR and bring in the pre-release/metadata commit and leave the library changes.

[wraithan]

I have no issues compiling or running this project and switching the library is unexpected in a PR that just mentions "updates dependencies" with no explanation of what the crash was, why change libraries, or anything. I have to reject this PR as a whole until that is explained or removed from the PR.

[gyscos]

At the time tomllib was crashing when parsing my Cargo.toml. I assumed it was caused by the metadata, but trying again it seems to be something else: it fails to parse nested objects like this:

[dependencies]
foo = "0.1"
bar = "0.2"

[dependencies.baz]
version = "0.3"

Might be joelself/tomllib#1

I mostly picked toml_edit as replacement because that's what cargo-edit uses.

[wraithan]

Can you make this PR solely about pre-release and metadata switches and remove anything to do with replacing the library? It is (in my opinion) poor form to include two very different things in a PR. Now that you've provided a problem case I can open an issue and we can see if toml-edit makes the most sense in its own context.

[gyscos]

I added the library as I couldn't test it otherwise.
The PR is already split in 2 independant commits, you're welcome to cherry-pick one half if you prefer.

[wraithan]

I'll be using your metadata/pre_release code as a starting point. NewVersion has felt uncomfortable as the name of the enum for a bit. So I'll be reworking the pre_release and metadata to be passed along as part of a VersionModifier struct. I appreciate the work that went into this patch, including changing the library out to test.

Sorry I was suspicious about that library change. In the wake of what happened with dominictarr/event-stream#116 where a dependency was changed to attack a specific target and the lack detailed reasoning on the original PR left me unsure. I did switch to toml_edit but after refactoring the code to be testable to compare toml_edit and toml-rs I wasn't able to integrate your patch without mostly rewriting it.