initial Kotlin Multiplatform support

[gabrielittner]

This adds support to publish multiplatform projects to all configured targets and sets up the coordinates and pom according to our properties.

Also updated Dokka to 0.10.0 which adds experimental multiplatform support. Without that projects would have to configure some things manually to avoid all builds failing.

closes #57

[codecov]

Codecov Report

Merging #105 into master will decrease coverage by 1.22%.
The diff coverage is 4.87%.

@@             Coverage Diff              @@
##             master     #105      +/-   ##
============================================
- Coverage     36.67%   35.44%   -1.23%     
+ Complexity       50       49       -1     
============================================
  Files            21       22       +1     
  Lines           409      426      +17     
  Branches         67       70       +3     
============================================
+ Hits            150      151       +1     
- Misses          231      246      +15     
- Partials         28       29       +1

Impacted Files	Coverage Δ	Complexity Δ
...vanniktech/maven/publish/MavenPublishConfigurer.kt	0% <0%> (ø)	0 <0> (ø)	⬇️
.../vanniktech/maven/publish/tasks/EmptySourcesJar.kt	0% <0%> (ø)	0 <0> (?)
...nniktech/maven/publish/UploadArchivesConfigurer.kt	85.29% <0%> (-2.59%)	10 <0> (ø)
...vanniktech/maven/publish/BaseMavenPublishPlugin.kt	61.36% <40%> (-3.64%)	5 <0> (ø)

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[vanniktech]

This is dope. Would @Egorand be willing to give it a try?

[gabrielittner]

I forgot to mention that I've tested this with a local snapshot on SqlDelight. sqldelight/sqldelight@master...gabrielittner:publish-plugin
One thing that needs to happen for everything to work is updating Dokka in SqlDelight (my local snapshot was still using 0.9.x). Running the branch above with this pr would cause dokka to fail.

[vanniktech]

Oh wow. That's even neater.

[Egorand]

This is awesome!

[Egorand]

nit: Multiplatform -> KotlinMultiplatform?

[gabrielittner]

Makes sense #112