Generate .cz.yaml that comply yamllint

[Lee-W]

Description

• feat(yaml_config): add explicit_start for yaml output
• ci(pre-commit): set linter and test stage to push stage
• ci(scripts): add -nr 3 to commitizen commit check

Checklist

• Add test cases to all the changes you introduce
• Run ./scripts/format and ./scripts/test locally to ensure this change passes linter check and test
• Test the changes on the local machine manually
• Update the documentation for the changes

Expected behavior

cz init generates cz.yaml that complys yamllint

Steps to Test This Pull Request

1. cz init
2. choose .cz.yaml or cz.yaml
3. install yamllint
4. yamllint cz.yaml or yamllint .cz.yaml

Additional context

#618

[codecov]

Codecov Report

Base: 97.92% // Head: 97.92% // No change to project coverage 👍

Coverage data is based on head (619e2d2) compared to base (db42a95).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head 619e2d2 differs from pull request most recent head 0c807f3. Consider uploading reports for the commit 0c807f3 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #630   +/-   ##
=======================================
  Coverage   97.92%   97.92%           
=======================================
  Files          35       35           
  Lines        1252     1252           
=======================================
  Hits         1226     1226           
  Misses         26       26           

Flag	Coverage Δ
unittests	97.92% <100.00%> (ø)

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

Impacted Files	Coverage Δ
commitizen/__version__.py	100.00% <100.00%> (ø)
commitizen/commands/changelog.py	98.86% <100.00%> (ø)
commitizen/config/yaml_config.py	100.00% <100.00%> (ø)

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[Lee-W]

@woile I've rebased this one again. Could you please take a look when you have time? Thanks!