docs(README): update documentation site link text

Author: bearomorphism

docs/README.md

@@ -12,7 +12,7 @@
 
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-**Documentation:** [https://commitizen-tools.github.io/commitizen/](https://commitizen-tools.github.io/commitizen/)
+[**Commitizen Documentation Site**](https://commitizen-tools.github.io/commitizen/)
 
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