[#49] Specify which version of the tool was actually downloaded

[MitchellBerend]

This resolves #49

I took a stab at implementing this but Im not sure if my approach is the right
way to go. Because the list of tools is already known before actually calling
the github api the length of these names is also known. This is not that case
with the tag_name. The tags from the example file are all less than 7 long but
that does not guarantee other repos.

I could try and check what tags are available for all tools before actually
downloading them. Can I get your input on this?

$ cargo run -- --config tools.toml sync
    Finished dev [unoptimized + debuginfo] target(s) in 0.02s
     Running `target/debug/tool --config tools.toml sync`
✅  bat        v0.21.0  Completed!
✅  difftastic 0.34.0   Completed!
✅  exa        v0.10.1  Completed!
✅  fd         v8.4.0   Completed!
✅  ripgrep    13.0.0   Completed!

[chshersh]

@MitchellBerend Wow, thanks a lot for working on this! I'll have a look as soon as I can 🤗

[MitchellBerend]

#61 might actually solve the issue that I have with my pr since it does actually give some idea about the length of the tag before the program reaches out to github. We can maybe assume latest as the lower bound and the longest tag as the upper bound like you did with max_tool_size

[chshersh]

@MitchellBerend Thanks a lot for the implementation!

I think this change is good on its own so I'm happy to merge it 👏🏻
Further improvements can be done after #32 is fixed (for example, it would be nice to see the version during the Downloading phase as well). But I propose to do this after #61 merged 🚢