doc: fix a typo in the Integrations/CI documentation

[NielsPilgaard]

Description

This PR solves a typo in the Integrations/CI documentation.

Correction: npm add -g @unlighthouse/cli puppeteer -> npm install -g @unlighthouse/cli puppeteer

Pipeline that fails to use Unlighthouse with npm add -g @unlighthouse/cli puppeteer

• https://github.com/NielsPilgaard/Jordnaer/actions/runs/5098092340/jobs/9165031035

Pipeline that successfully uses Unlighthouse with npm install -g @unlighthouse/cli puppeteer

• https://github.com/NielsPilgaard/Jordnaer/actions/runs/5098112456/jobs/9165064644

The failure in the last link is not caused by Unlighthouse

Linked Issues

Additional context

[harlan-zw]

Thanks!