fix: typesafe testSaga & expectSaga

[ghost]

When used with typescript, I saw that testSaga and expectSaga functions were not typesafe with their parameters.

Just used the power of typescript generics to fix that :)

[codecov-io]

Codecov Report

Merging #270 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #270   +/-   ##
=======================================
  Coverage   99.59%   99.59%           
=======================================
  Files          22       22           
  Lines         744      744           
  Branches      153      153           
=======================================
  Hits          741      741           
  Misses          3        3

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[META-DREAMER]

@jfairbank @jp928 It would be incredibly useful if this could be merged. Could you have a look please?

[jp928]

@HammadJ @TheryFouchter Thanks for your contribution. This pull request has been merged.

[META-DREAMER]

@jp928 any idea when we could expect this to be released to NPM?

[jp928]

@HammadJ Thanks for your contribution. The 4.0.0-beta4 has been released.

[META-DREAMER]

@jp928 We are still using redux-saga 0.16.2, but 4.0.0 is only comparable with redux-saga > 1. Is there any chance you could release a patch for [email protected] with this change? Can release it as 3.7.1, or 3.8.0 to prevent people getting type errors?