Add documentation page on type resolution

[cortinico]

I'm adding a page to explain in detail what is type resolution, how to enable it, how to write a custom rule that uses it and how to test it 👌

We had an empty page on the website for too long :) To start filling it.
This page is more like a draft. Happy to collect and integrated feedbacks.

Fixes #2259

[codecov]

Codecov Report

Merging #3225 (f7d597a) into master (cd659ce) will decrease coverage by 0.04%.
The diff coverage is 77.63%.

@@             Coverage Diff              @@
##             master    #3225      +/-   ##
============================================
- Coverage     80.10%   80.06%   -0.05%     
- Complexity     2647     2649       +2     
============================================
  Files           440      443       +3     
  Lines          8013     8072      +59     
  Branches       1529     1535       +6     
============================================
+ Hits           6419     6463      +44     
- Misses          775      789      +14     
- Partials        819      820       +1     

Impacted Files	Coverage Δ	Complexity Δ
...n/io/github/detekt/report/sarif/RuleDescriptors.kt	21.05% <21.05%> (ø)	0.00 <0.00> (?)
...rbosch/detekt/rules/style/EqualsOnSignatureLine.kt	77.77% <71.42%> (-11.12%)	6.00 <5.00> (+1.00)	⬇️
...n/kotlin/io/github/detekt/report/sarif/SarifDsl.kt	100.00% <100.00%> (ø)	0.00 <0.00> (?)
...io/github/detekt/report/sarif/SarifOutputReport.kt	100.00% <100.00%> (ø)	3.00 <3.00> (?)
...ab/arturbosch/detekt/rules/empty/EmptyWhenBlock.kt	66.66% <0.00%> (-8.34%)	1.00% <0.00%> (-1.00%)
...rturbosch/detekt/rules/bugs/UnnecessarySafeCall.kt	71.42% <0.00%> (-3.58%)	3.00% <0.00%> (-1.00%)
...ab/arturbosch/detekt/formatting/KtLintMultiRule.kt	92.15% <0.00%> (-0.16%)	6.00% <0.00%> (-2.00%)
... and 2 more

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[BraisGabin]

Great addition!

[schalkms]

Sorry for the late review. I completely missed this PR.
Anyways, I really appreciate your work on this. This is great stuff. 👏
I have only some minor comments (typos, grammar).