Update types + add TS tests

[kale-stew]

Description

This PR
(1) introduces a file to more thoroughly test our type definitions
(2) introduces docs surrounding these tests
(3) update our TS guidelines
(4) Fixes our type defs where needed

Still running into an issue with timeout in the Preact beforeEach

Closes #69

Checklist:

• All tests are passing
• Benchmark performance has not significantly decreased (tests won't affect benchmarks)
• Bundle size has not been significantly impacted (^)
• The bundle size badge has been updated to reflect the new size (won't be necessary)

[codecov-commenter]

Codecov Report

Merging #77 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #77   +/-   ##
=======================================
  Coverage   98.21%   98.21%           
=======================================
  Files           1        1           
  Lines          56       56           
=======================================
  Hits           55       55           
  Misses          1        1           

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[chrisbolin]

just a few things. should all be pretty minor

[chrisbolin]

NOTE: as is this will not close #61, so we should make sure that doesn't happen. A test for #61 can be added in a new PR (this one is big enough :) )

[ryan-roemer]

Just some cleanup comments after which LGTM!

[ryan-roemer]

Lint failures in appveyor:

24C:\projects\react-fast-compare\test\typescript\sample-usage.tsx
25  23:7  error  'TestChild' is defined but never used      no-unused-vars
26  34:7  error  'TestContainer' is defined but never used  no-unused-vars

[ryan-roemer]

I think a simple export of test container will fix the error. Bigger question is why Travis didn’t flag the failure

[kale-stew]

We intentionally pulled tslint out of the test script yesterday because we didn't want to muck around in lint configs for our test files for too long, but this morning the issue has been identified as a react-specific lint plugin which I've now introduced. tslint is back into our CI script, and this push ^ should fix things

[chrisbolin]

nice work! and thanks for creating #79 so we can return to the linting question later