build: add ktlint

[stuebingerb]

Adds ktlint for style checking, and enables selected rules as starting point.

[codecov]

Codecov Report

❌ Patch coverage is 60.71429% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.86%. Comparing base (11885cb) to head (1e43cb6).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ebase/kgraphql/schema/dsl/DataLoaderPropertyDSL.kt	0.00%	3 Missing ⚠️
.../apurebase/kgraphql/schema/dsl/UnionPropertyDSL.kt	0.00%	3 Missing ⚠️
...n/com/apurebase/kgraphql/schema/dsl/PropertyDSL.kt	33.33%	1 Missing and 1 partial ⚠️
...apurebase/kgraphql/schema/dsl/KotlinPropertyDSL.kt	50.00%	0 Missing and 1 partial ⚠️
...ase/kgraphql/schema/structure/SchemaCompilation.kt	66.66%	0 Missing and 1 partial ⚠️
...in/nidomiro/kdataloader/TimedAutoDispatcherImpl.kt	80.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #453      +/-   ##
==========================================
+ Coverage   82.83%   82.86%   +0.02%     
==========================================
  Files         152      152              
  Lines        4796     4797       +1     
  Branches      851      852       +1     
==========================================
+ Hits         3973     3975       +2     
+ Misses        515      514       -1     
  Partials      308      308              

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