feat(cluster): add calculator option

[whythecode]

adds support for defining a custom calculator function

resolves #1510
relates to #1349

[codecov]

Codecov Report

Merging #1599 into master will increase coverage by 0.21%.
The diff coverage is 40%.

@@            Coverage Diff             @@
##           master    #1599      +/-   ##
==========================================
+ Coverage   30.43%   30.64%   +0.21%     
==========================================
  Files          36       36              
  Lines        1531     1540       +9     
  Branches      123      125       +2     
==========================================
+ Hits          466      472       +6     
- Misses       1063     1066       +3     
  Partials        2        2

Impacted Files	Coverage Δ
...s/js-marker-clusterer/directives/marker-cluster.ts	0% <0%> (ø)	⬆️
...ker-clusterer/services/managers/cluster-manager.ts	55.07% <47.05%> (+4.27%)	⬆️

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[whythecode]

@SebastianM ich schulde dir einen Kaffee wenn du's bald mergen und deployen kannst :)

[sebholstein]

thx for the MR. Added some comments. I'm happy to merge it when the comments are addressed

[whythecode]

awesome, thanks @SebastianM ! the comments have been fixed

[sebholstein]

thanks

[whythecode]

awesome, thanks a lot @SebastianM !

[whythecode]

hi @SebastianM , any chance there will be a release the next couple of weeks? would be great if you could just let me know (no matter whether yes or no), so that I can plan accordingly. thanks!!

[popcris8gm]

Hello @SebastianM.

First of all, you did a great job here, awesome!
But I saw you committed the code with 'custom calculator' but it is not released... How exactly I can use it?
I would appreciate your help