Allow calling recomputeTree without arguments

[Lodin]

This PR allows to call FixedSizeTree#recomputeTree and VariableSizeTree#recomputeTree methods without arguments. It addresses the issue raised in #7 (comment).

You can use it in the following way:

await tree.recomuteTree();

Default options for FixedSizeTree are:

const options = {
  refreshNodes: false,
  useDefaultOpenness: false,
};

Default options for VariableSizeTree are:

const options = {
  refreshNodes: false,
  useDefaultHeight: false,
  useDefaultOpenness: false,
};

Also, this PR updates all dependencies and refactors code to use optional chaining and the Typescript stricter generators.

[codecov]

Codecov Report

Merging #8 into master will decrease coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master       #8      +/-   ##
==========================================
- Coverage   99.27%   99.26%   -0.02%     
==========================================
  Files           3        3              
  Lines         138      136       -2     
  Branches       30       28       -2     
==========================================
- Hits          137      135       -2     
  Misses          1        1

Impacted Files	Coverage Δ
src/utils.tsx	100% <ø> (ø)	⬆️
src/VariableSizeTree.tsx	98.71% <100%> (-0.04%)	⬇️
src/FixedSizeTree.tsx	100% <100%> (ø)	⬆️

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