docs: update README.md

[xiaojianzhong]

Correct extend's name.

Motivation and Context

The installed extend is @commitlint/angular while the required extend is @commitlint/conventional.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[escapedcat]

Thanks for noticing! According to the docs it should be this I guess:

npm install --save-dev @commitlint/{cli,config-conventional,prompt-cli}
echo "module.exports = {extends: ['@commitlint/config-conventional']};" > commitlint.config.js

What do you think?

[xiaojianzhong]

Okay, i have replaced @commitlint/config-angular with @commitlint/config-conventional by force pushing.