docs(README.md): adds missing link

[edvm]

Description

Adds missing links on README.md

Checklist

• Add test cases to all the changes you introduce
• Run ./script/format and ./script/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

Steps to Test This Pull Request

Additional context

[codecov]

Codecov Report

Merging #308 (bf4621c) into master (720befe) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #308   +/-   ##
=======================================
  Coverage   96.96%   96.97%           
=======================================
  Files          33       33           
  Lines         924      926    +2     
=======================================
+ Hits          896      898    +2     
  Misses         28       28           

Flag	Coverage Δ
unittests	96.97% <100.00%> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
commitizen/__version__.py	100.00% <100.00%> (ø)
commitizen/commands/bump.py	94.44% <100.00%> (+0.12%)	⬆️

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[woile]

we want to leave the url, so it should be more like:

[commitizen-tools.github.io/commitizen/](https://commitizen-tools.github.io/commitizen/)