dev: include basic clj-kondo config

[lread]

Like eastwood, clj-kondo can help to find mistakes, but it can do so while you edit source. A very tight feedback loop!

This PR adds a basic clj-kondo config. It tells clj-kondo:

• to interpret MrAnderson test macros like Clojure's let
• that it is ok that MrAnderson code cond default is not :else (MrAnderson uses :default)
• to not warn on unused destructured keys

Also:

• clj-kondo found an unused import. Turfed it.

[codecov-commenter]

Codecov Report

Base: 64.31% // Head: 64.31% // No change to project coverage :thumbsup:

Coverage data is based on head (4349e6e) compared to base (8bbb87d). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #70 +/- ## ======================================= Coverage 64.31% 64.31% ======================================= Files 7 7 Lines 709 709 Branches 50 50 ======================================= Hits 456 456 Misses 203 203 Partials 50 50 ``` | [Impacted Files](https://codecov.io/gh/benedekfazekas/mranderson/pull/70?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Benedek+Fazekas) | Coverage Δ | | |---|---|---| | [src/mranderson/util.clj](https://codecov.io/gh/benedekfazekas/mranderson/pull/70/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Benedek+Fazekas#diff-c3JjL21yYW5kZXJzb24vdXRpbC5jbGo=) | `55.30% <ø> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Benedek+Fazekas). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Benedek+Fazekas)

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[benedekfazekas]

thanks