Types for transformed explorer

[manferlo81]

I am using this package in one of my typescript projects, I noticed an Explorer (or ExplorerSync) search and load methods signature does not change even if you use the transform option, this PR fixes that. I kept the original signature as fallback so no code will be broken. This is not a functionality issue it's a types issue, the methods work as intended, just the types are wrong.

Note that this is a "quick and easy" fix, there are a lot of improvement that can be done "typeswise". I tried to keep all changes contained so it's easy to review.

[codecov-io]

Codecov Report

Merging #234 into master will not change coverage by %. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #234   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            9         9           
  Lines          227       227           
  Branches        46        46           
=========================================
  Hits           227       227           

Impacted Files	Coverage Δ
src/index.ts	100.00% <100.00%> (ø)

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