Support findByIds() query

[cvara]

Adds support for findByIds() query.

Things that need to be resolved before merging:

• Fix Silence typescript issues (ts2349)
• Homogenize promise/observable result handling
• Does pagination make sense when using findByIds()? Answer: No, pagination is ignored when using findByIds()
• Abort promise on component cleanup (aka handle component unmount before promise resolves)
• Get to 100% coverage

Fixes #46

[codecov]

Codecov Report

Merging #47 (52c4133) into master (074cd6b) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #47   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            7         8    +1     
  Lines          131       160   +29     
  Branches        29        37    +8     
=========================================
+ Hits           131       160   +29     

Impacted Files	Coverage Δ
src/useRxData.ts	100.00% <ø> (ø)
src/helpers.ts	100.00% <100.00%> (ø)
src/useRxQuery.ts	100.00% <100.00%> (ø)

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