Improves the docs on derive

[xd009642]

So I've done a bit of work to improve the derive docs.

I do think another improvement may be to copy the style done in the tokio docs and for some simple examples show how the generated code looks. However, I think fake would benefit less from this compared to tokio (how a runtime is setup for an async application is important to more people). So it may just add unnecessary noise to the docs. I've refrained from doing that but if you think it's an improvement just let me know and I can add it easily 😄

Fixes #138

[cksac]

I think showing the expanded code in doc not that useful. we can show more usage of the Dummy attribute,
e.g

1. type not implement by Faker, A constructor fn attribute for 3rd party types?  #102 (comment)
2. expr https://github.com/cksac/fake-rs/blob/master/fake/examples/derive.rs#L76
3. default https://github.com/cksac/fake-rs/blob/master/fake/examples/derive.rs#L85
4. config vec, https://github.com/cksac/fake-rs/blob/master/fake/examples/derive.rs#L23
5. non None options, Is there a way to force all Option members to be Some(foo)? #139

[xd009642]

For 5. how can that functionality be accessed via the derive? It's not clear from me looking at the issue and there's no related links to jump off of 👀.

And sure I'll start adding these extra bits after work 👍

[cksac]

ya, item 5 might belong to general doc

[xd009642]

I've addressed 1, 2, 3 and 5. Looking into config vec now

[xd009642]

Okay added config vec into the lib.rs module docs, I felt it made more sense there than in the macro docs. It's kind of a weird one I guess it's down to FakeBase that I can't see the tuples in any trait implementations. Sealed traits do have that downside on doc discoverability 😅

Let me know any feedback, and as a side note any idea when the next release will go out? Would like to start using things added in my last PRs without relying on a git dep 👀

[cksac]

looks good to me. Next release will be this week.