feat: add 'testing' preset

[moul]

No description provided.

[github-actions]

Expected release notes (by @moul)

features:
add 'testing' preset (6317010)

others (will not be included in Semantic-Release notes):
bump codfish/semantic-release-action from 1 to 1.9.0 (6af2655)
bump actions/checkout from 2 to 2.3.4 (74a41b9)
bump codecov/codecov-action from 1 to 1.5.0 (fcc70ea)
add a New() constructor + update examples (33ac2dd)
bump actions/cache from v2.1.4 to v2.1.5 (84f982e)
bump golangci/golangci-lint-action from v2.5.1 to v2.5.2 (bf2d63e)
bump golangci/golangci-lint-action from v2.4.0 to v2.5.1 (1abf8f0)
bump golangci/golangci-lint-action from v2 to v2.4.0 (dbf312f)
bump actions/cache from v2 to v2.1.4 (fec4a71)
bump moul.io/u from 1.19.1 to 1.20.0 (14d2284)
bump moul.io/u from 1.19.0 to 1.19.1 (80cb8c3)

• I hereby acknowledge these release notes are 🥙 AWESOME 🥙

[codecov]

Codecov Report

Merging #33 (6317010) into master (5509d81) will increase coverage by 2.13%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #33      +/-   ##
==========================================
+ Coverage   70.78%   72.91%   +2.13%     
==========================================
  Files           2        2              
  Lines          89       96       +7     
==========================================
+ Hits           63       70       +7     
  Misses         25       25              
  Partials        1        1              

Flag	Coverage Δ
unittests	72.91% <100.00%> (+2.13%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
encoder.go	36.84% <ø> (+3.50%)	⬆️
zapconfig.go	81.81% <100.00%> (+1.53%)	⬆️

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[github-actions]

🎉 This PR is included in version 1.4.0 🎉

The release is available on GitHub release

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