Add config of list indent size

[egs33]

This PR is related to #8.

Add config of list indent size.
If this config is set to 1. Codes is formatted as below.

(foo
 bar
 baz)

[codecov-io]

Codecov Report

Merging #21 into master will increase coverage by 0.02%.
The diff coverage is 92.85%.

@@            Coverage Diff             @@
##           master      #21      +/-   ##
==========================================
+ Coverage   73.97%   73.99%   +0.02%     
==========================================
  Files          10       10              
  Lines        1145     1146       +1     
  Branches       27       27              
==========================================
+ Hits          847      848       +1     
  Misses        271      271              
  Partials       27       27

Impacted Files	Coverage Δ
core/src/cljstyle/config.clj	98.09% <100%> (+0.01%)	⬆️
core/src/cljstyle/format/core.clj	97.05% <100%> (ø)	⬆️
core/src/cljstyle/format/indent.clj	94.07% <88.88%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6b14b69...8a71ff2. Read the comment docs.

[egs33]

clojure-style-guide suggested one space indent.

This PR enable its style.

[greglook]

This is great, thanks for tackling this! Based on the number of 👍 votes on #8 this will definitely be a popular feature. I have some comments on style and some consistency questions, but the logic generally seems sound. Once those small things are fixed it'll be good to go.

(Thanks for your patience on the review, I've been AFK travelling for a few weeks.)

[greglook]

This is a significant enough setting that it probably belongs higher up, directly under :indentation?.

[greglook]

Consistently placing this key after :indentation? would be helpful too.

[greglook]

I'll just note here that there's some inconsistency in how this argument is ordered throughout the rest of the changes here. Some places have it as a new final argument like this, others take it as a new second argument. Since this is the more basic of the two configuration arguments here, I think you should consistently place list-indent-size before indents and (later) the indenter rule arguments. That will also let you keep some partial forms intact later on.

[greglook]

An example of the ordering inconsistency I mentioned above.

[greglook]

Thanks for adding some new tests! The rest of the test code would have many fewer changes if you kept the two-argument version as-is accepting indents and used the three-argument version for the list-indent-size when you needed it. Seems like a lot of the existing tests just got a 2 inserted.

[egs33]

Thanks for reviewing. I fixed them. Please re-review.

[greglook]

Looks good!