Add support for ktfmt

[0x26res]

Here's the help for ktfmt:

$ java -jar ./ktfmt-0.46-jar-with-dependencies.jar  --help
Usage: ktfmt [--dropbox-style | --google-style | --kotlinlang-style] [--dry-run] [--set-exit-if-changed] [--stdin-name=<name>] [--do-not-remove-unused-imports] File1.kt File2.kt ...

Some notes:

• nitpick: should we use consistent case for ktlint all lower case. I see KTLint/KTlint is used in places, but I don't see it spelled this way in the official repo. Also it seems ktfmt is always spelled in lower case.
• ktfmt autofix by default, but has a --dry-run mode which I use by default (and turn off with --autofix
• ktfmt also needs --set-exit-if-changed to be turned on so we get consistent error code (fail if a file is badly formatted)
• I'm getting the ktfmt jar from maven, I couldn't find it on github
• we should run black on this repo to format the code. I find it ironic that its code is not formatted (maybe in another PR).
• great test, it took me some time to wrap my head around them, but then it's easy to add to them.

[0x26res]

Thanks for the feedback and spending the time to explain everything.

👍

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (23ad93b) 100.00% compared to head (9c2d33a) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #196 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 10 10 Lines 317 333 +16 ========================================= + Hits 317 333 +16 ```

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[0x26res]

@macisamuele I was trying to test locally and realized I was missing a data file. See my PR: https://github.com/macisamuele/language-formatters-pre-commit-hooks/pull/199